This PowerPoint wants to explore the bird's eye view of the reproduction of bacteria in general and the genetic recombination of bacteria in particular.
Introduction,In some fungi ,true sexual cycle comprising of nuclear fusion and meiosis is absent.
These fungi derive the benefits of sexuality through a cycle know as parasexuaL cycle.
First Reported by- Gudio Pontecorvo and J.A.Roper(1952)
Parasexual cycle was reported in
Aspergillus nidulans,the imperfect stage of Emericella nidulans.
Since then parasexual cycle has been discovered not only in several members of Deutromycetes but also in fungi belonging to Ascomycetes and Basidiomycetes.
DEFINETION - Parasexuality is defined as a cycle in which Plasmogamy, Karyogamy and Meiosis [Haploidization] take place in sequence but not at a specified time or at specified points in the life cycle of an organism.
Generally parasexual cycle occurs in those fungi in which true sexual cycle does not take place.
Parasexualcycle also know as Somatic recombination. PASEXUALITY ALSO REPORTED IN SOME ORGANISMS- Aspergillus nigar, Penicillium crysogenum, STEPS OF PARASEXUAL CYCLE - 1) ESTABLISHMENT OF HETEROKARYOSIS, 2) Formation of Heterozygous DIPLOIDS, 3) occasional mitotic crossing-over during multiplication of diploid nuclei, 4)occasional haplodization through aneuploidy , COMPARISION BETWEEN SEXUAL AND PARASEXUAL CYCLE, IMPORTANCE OF PARASEXUALITY, C0NCLUSION
TOBACCO MOSAIC VIRUS (Genome organization &their replication) TMV is a plant virus which infects a wide range of plants, especially tobacco and other members of the family Solanaceae and cucumbers, and a number of ornamental flowers.
Introduction,In some fungi ,true sexual cycle comprising of nuclear fusion and meiosis is absent.
These fungi derive the benefits of sexuality through a cycle know as parasexuaL cycle.
First Reported by- Gudio Pontecorvo and J.A.Roper(1952)
Parasexual cycle was reported in
Aspergillus nidulans,the imperfect stage of Emericella nidulans.
Since then parasexual cycle has been discovered not only in several members of Deutromycetes but also in fungi belonging to Ascomycetes and Basidiomycetes.
DEFINETION - Parasexuality is defined as a cycle in which Plasmogamy, Karyogamy and Meiosis [Haploidization] take place in sequence but not at a specified time or at specified points in the life cycle of an organism.
Generally parasexual cycle occurs in those fungi in which true sexual cycle does not take place.
Parasexualcycle also know as Somatic recombination. PASEXUALITY ALSO REPORTED IN SOME ORGANISMS- Aspergillus nigar, Penicillium crysogenum, STEPS OF PARASEXUAL CYCLE - 1) ESTABLISHMENT OF HETEROKARYOSIS, 2) Formation of Heterozygous DIPLOIDS, 3) occasional mitotic crossing-over during multiplication of diploid nuclei, 4)occasional haplodization through aneuploidy , COMPARISION BETWEEN SEXUAL AND PARASEXUAL CYCLE, IMPORTANCE OF PARASEXUALITY, C0NCLUSION
TOBACCO MOSAIC VIRUS (Genome organization &their replication) TMV is a plant virus which infects a wide range of plants, especially tobacco and other members of the family Solanaceae and cucumbers, and a number of ornamental flowers.
The simplest virions consist of two basic components: nucleic acid (single- or double-stranded RNA or DNA) and a protein coat, the capsid, which functions as a shell to protect the viral genome from nucleases and which during infection attaches the virion to specific receptors exposed on the prospective host cell.
Major divisions in Bergey's manual of systematic bacteriology 2nd edition presented for examination purpose. Pinned important points are compiled here for students.
Ribotyping
Introduction
History
Ribosomes
Ribosomal RNA
Principle of ribotyping
16S rRNA
Procedure of ribotyping
Types of ribotyping
Use of ribotyping
Advantage and disadvantage of ribotyping
Reference
Bergey's Manual and it's classification. A brief concised presentation prepared for taking seminar and classes.
Volume II (Edition 2) described more in detail.
Heterothallic species have sexes that reside in different individuals. . The term is applied particularly to distinguish heterothallic fungi, which require two compatible partners to produce sexual spores, from homothallic ones, which are capable of sexual reproduction from a single organism.
The simplest virions consist of two basic components: nucleic acid (single- or double-stranded RNA or DNA) and a protein coat, the capsid, which functions as a shell to protect the viral genome from nucleases and which during infection attaches the virion to specific receptors exposed on the prospective host cell.
Major divisions in Bergey's manual of systematic bacteriology 2nd edition presented for examination purpose. Pinned important points are compiled here for students.
Ribotyping
Introduction
History
Ribosomes
Ribosomal RNA
Principle of ribotyping
16S rRNA
Procedure of ribotyping
Types of ribotyping
Use of ribotyping
Advantage and disadvantage of ribotyping
Reference
Bergey's Manual and it's classification. A brief concised presentation prepared for taking seminar and classes.
Volume II (Edition 2) described more in detail.
Heterothallic species have sexes that reside in different individuals. . The term is applied particularly to distinguish heterothallic fungi, which require two compatible partners to produce sexual spores, from homothallic ones, which are capable of sexual reproduction from a single organism.
Bacteria are the simplest, the smallest, and the most successful microorganisms.
They were first discovered by Anton Leeuwenhoek (1676).
In the five kingdom classification, they are placed in Kingdom Monera. Reproduction: Vegetative Reproduction, Sexual Reproduction & Asexual Reproduction.
Prokaryotes can exchange DNA with eukaryotes, although the mechanisms behind this process are not well understood. Suspected mechanisms include conjugation and endocytosis, such as when a eukaryotic cell engulfs a prokaryotic cell and gathers it into a special membrane-bound vesicle for degradation.
This presentation explores a brief idea about the structural and functional attributes of nucleotides, the structure and function of genetic materials along with the impact of UV rays and pH upon them.
This presentation intends to explore the communication of the cell within and others for sustainability along the regulation mechanisms by the cellular neural networks and others to sing the song of the life.
Bioenergetics is an important domain in biology. This presentation has explored ATP production and its optimum utilization in biological systems along with certain theories and experiments to give a bird's eye view of this important issue.
This presentation offers the bird's eye view of the cell as the basic structural and functional unit of life. It also addresses the origin of eukaryotic cells from the prokaryotic cell by the endosymbiotic theory.
This presentation has been intended to offer a bird's eye view about the phylogenetic classification of the plant kingdom in general and the Engler and Prantl system in particular with merits and demerits.
This PPT has been made to explore the plant classification in general and the classification as made by Bentham & Hooker for the classification of the flowering plants. It also offers the history of plant classification along with the merits and demerits of this aforesaid classification.
Energy and the biological systems are joined together and no biological world is almost impossible without ATP. This study material intends to explore the beauty of ATP to drive different biological processes.
This PPT offers a bird's eye view of ICBN and its different rules along with regulations for the naming of plants. It also highlights the history of IBC and its contribution to plant taxonomy.
This presentation intends to offer the basic features of plant metabolism along with the different types of mechanisms to regulate and control the metabolic pathways.
This presentation has been designed to give the foundation of taxonomy in general and Plant Taxonomy in particular as a matter of pleasure to explore the diversity of the plant world.
Sex and sexuality are very common words in biology but para-sexuality is a little bit uncommon, several organisms in general and fungi in particular have the pleasure of sexuality to bring variations by beside sex. This PPT explores the beauty of para-sexuality for the academic fraternity.
Sex life in fungi is not less fascinating than in other organisms. Heterosexuality is a matter of pleasure to explore the diversity of sex in fungi along with its cause and consequences. You can find a pleasure to go through the content.
This presentation gives the bird's eye view of bacterial nutrition along with some other issues required to understand bacterial diversity as far as nutrition is concerned.
This presentation explores the food value of mushrooms along with the long-term and short-term storage procedures. It also offers a detailed account of the nutrients that remain present in the edible mushrooms.
If you want to explore the role of Cyanobacteria in soil fertility in general & Azolla-Anabena association in particular, you can visit this PowerPoint Presentation.
Nutraceutical market, scope and growth: Herbal drug technologyLokesh Patil
As consumer awareness of health and wellness rises, the nutraceutical market—which includes goods like functional meals, drinks, and dietary supplements that provide health advantages beyond basic nutrition—is growing significantly. As healthcare expenses rise, the population ages, and people want natural and preventative health solutions more and more, this industry is increasing quickly. Further driving market expansion are product formulation innovations and the use of cutting-edge technology for customized nutrition. With its worldwide reach, the nutraceutical industry is expected to keep growing and provide significant chances for research and investment in a number of categories, including vitamins, minerals, probiotics, and herbal supplements.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Cancer cell metabolism: special Reference to Lactate PathwayAADYARAJPANDEY1
Normal Cell Metabolism:
Cellular respiration describes the series of steps that cells use to break down sugar and other chemicals to get the energy we need to function.
Energy is stored in the bonds of glucose and when glucose is broken down, much of that energy is released.
Cell utilize energy in the form of ATP.
The first step of respiration is called glycolysis. In a series of steps, glycolysis breaks glucose into two smaller molecules - a chemical called pyruvate. A small amount of ATP is formed during this process.
Most healthy cells continue the breakdown in a second process, called the Kreb's cycle. The Kreb's cycle allows cells to “burn” the pyruvates made in glycolysis to get more ATP.
The last step in the breakdown of glucose is called oxidative phosphorylation (Ox-Phos).
It takes place in specialized cell structures called mitochondria. This process produces a large amount of ATP. Importantly, cells need oxygen to complete oxidative phosphorylation.
If a cell completes only glycolysis, only 2 molecules of ATP are made per glucose. However, if the cell completes the entire respiration process (glycolysis - Kreb's - oxidative phosphorylation), about 36 molecules of ATP are created, giving it much more energy to use.
IN CANCER CELL:
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
introduction to WARBERG PHENOMENA:
WARBURG EFFECT Usually, cancer cells are highly glycolytic (glucose addiction) and take up more glucose than do normal cells from outside.
Otto Heinrich Warburg (; 8 October 1883 – 1 August 1970) In 1931 was awarded the Nobel Prize in Physiology for his "discovery of the nature and mode of action of the respiratory enzyme.
WARNBURG EFFECT : cancer cells under aerobic (well-oxygenated) conditions to metabolize glucose to lactate (aerobic glycolysis) is known as the Warburg effect. Warburg made the observation that tumor slices consume glucose and secrete lactate at a higher rate than normal tissues.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Richard's entangled aventures in wonderlandRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
The increased availability of biomedical data, particularly in the public domain, offers the opportunity to better understand human health and to develop effective therapeutics for a wide range of unmet medical needs. However, data scientists remain stymied by the fact that data remain hard to find and to productively reuse because data and their metadata i) are wholly inaccessible, ii) are in non-standard or incompatible representations, iii) do not conform to community standards, and iv) have unclear or highly restricted terms and conditions that preclude legitimate reuse. These limitations require a rethink on data can be made machine and AI-ready - the key motivation behind the FAIR Guiding Principles. Concurrently, while recent efforts have explored the use of deep learning to fuse disparate data into predictive models for a wide range of biomedical applications, these models often fail even when the correct answer is already known, and fail to explain individual predictions in terms that data scientists can appreciate. These limitations suggest that new methods to produce practical artificial intelligence are still needed.
In this talk, I will discuss our work in (1) building an integrative knowledge infrastructure to prepare FAIR and "AI-ready" data and services along with (2) neurosymbolic AI methods to improve the quality of predictions and to generate plausible explanations. Attention is given to standards, platforms, and methods to wrangle knowledge into simple, but effective semantic and latent representations, and to make these available into standards-compliant and discoverable interfaces that can be used in model building, validation, and explanation. Our work, and those of others in the field, creates a baseline for building trustworthy and easy to deploy AI models in biomedicine.
Bio
Dr. Michel Dumontier is the Distinguished Professor of Data Science at Maastricht University, founder and executive director of the Institute of Data Science, and co-founder of the FAIR (Findable, Accessible, Interoperable and Reusable) data principles. His research explores socio-technological approaches for responsible discovery science, which includes collaborative multi-modal knowledge graphs, privacy-preserving distributed data mining, and AI methods for drug discovery and personalized medicine. His work is supported through the Dutch National Research Agenda, the Netherlands Organisation for Scientific Research, Horizon Europe, the European Open Science Cloud, the US National Institutes of Health, and a Marie-Curie Innovative Training Network. He is the editor-in-chief for the journal Data Science and is internationally recognized for his contributions in bioinformatics, biomedical informatics, and semantic technologies including ontologies and linked data.
1. A Presentation by
Dr. N. Sannigrahi,
Associate Professor,
Department of Botany,
Nistarini college, Purulia
( NAAC Accredited ‘A” Grade)
D.B. Road, Purulia (W.B)
723101, India
2.
3. Unicellular organisms do not undergo reproduction like the multicellular
one and the story of the prokaryotes quite different from the rest neither in
mode nor in the complexity. Reproduction in bacteria is simply the
multiplication in number either by vegetative and asexual method. There is
no sexual reproduction neither by the formation of sex organ's followed by
the gametes nor by the fusion of the non-identical gamets.But in some
cases, objective of usual reproduction for the reassortment of the genes
takes place but this process is quite dissimilar from the rest. Mainly three
types of reproduction noted:
Vegetative method-Only by the cell itself without any kind of
specialization
Asexual method-Cell undergone modification by the dint of some
specialized structure to address the harsh environment
Sexual method-this is not truly sexual one due to lack of desirable
specialization, rather it is the process of the recombination of genes in the
true sense.
4. The vegetative method mostly executed by the decisive use of the body cell
followed by a certain degree of modification. It occurs by three methods-
Budding,
Fragmentation,
Binary fission.
BUDDING:
a. small protuberance called bud at one end of the cell forms,
b. Genome replication occurs and copy of the replicated genome enters into
the bud,
c. The bud undergoes enlargement and finally the bud gets separated from
the parent cell
d. The bud gives the formation of new cell.
5. FRAGMENTATION
During unfavorable condition, protoplasm undergoes compartmentalization
forming minute bodies called gonidia,
Each gonidium now grows to a new bacterium under favorable condition,
Prior to the formation of gonidium, genome undergoes replication to
increase the DNA content.
BINARY FISSION
The cell contents become doubled,
DNA replication occurs , DNA undergoes partition and cross wall
formation takes place,
Bacterial chromosome gets attached to the cell membrane and replicated
into two,
The daughter DNA still attached to the cell wall and get separated by a
simple pinching off process,
6.
7. A cross wall is formed. The transverse plasma membrane is laid down
followed by the centripetal growth of the cell wall and splits the plasma
membrane into two halves.
The good environmental condition favors this process and 20-30 minutes
are enough to multiply the cell,
The binary fission enables the bacteria to multiply in geometric progression
to form a big bacterial colony within a short span.
The large group of bacteria called Actinomycetes form branching hyphae;
spores develop , singly or chain , from the tips of these hyphae by
crosswall.If they enclosed in sac called sporangiospores and if not they are
called conidiophores. Very often, cyst, thick walled desiccation resistant
forms develop by the differentiation of vegetative cells and germinate
under suitable conditions as a part of reproduction.
8. During unfavorable condition, the bacteria undergoes asexual process of
reproduction and this is enabled by the formation of endospore by the
following methods: A pert of the protoplast becomes concentrated around
the genome,
A hard resistant wall is formed around it, the rest of the bacterial cell
undergoes degeneration,
Each endospore is either spherical, or cylindrical or ellipsoidal in shape,
Endospore is a resting spore undergoes a number of modification. The
outer layer is thin, delicate called –exosporium, followed by the spore coat.
Inner to spore coat, the cortex contains concentric rings of wall. Below the
cortex, the core cell wall is encircling the cell membrane and protoplasm,
9.
10. Under favorable condition, the endospore germinates by imbibing water,
activating the cytoplasm , synthesizing metabolites and swelling follows
the bursting of wall giving rise to the formation of new vegetative cell.
The endospore consists of the bacterial DNA, ribosome and large
amounts of dipicolinic acid. Dipicolinic acid is a spore-specific chemical
that appears to help in the ability for endospores to maintain dormancy.
This chemical accounts for up to 10% -15% of the spore's dry weight. It
occurs in combination with large amounts of calcium and probably located
in the core i.e. in the central part of the spore. The calcium-DPA complex
possibly play a vital role in the heat resistance of endospores. Synthesis of
DPA and the uptake of calcium occurs during advance stages of
sporulation.
11. Genetic recombination is a most dramatic episode in biological drama that
enables two genetic traits of two non-identical cells come together and
recombine in a manner and make the avenue of the formation of the 3rd cell
i.e. zygote to give the birth of new individual. It is one of the most
interesting biological process that acts expedite the biological evolution
process. The process of the genetic recombination in prokaryotes unlike
different from the eukaryotes. In bacteria, the sexual reproduction truly
absent but genetic recombination still prevails as a natural adaptation for
the new combination of genes. If the favorable new character is generated
by mutation, it spreads to the successors through this genetic
recombination. In bacteria, this process of mixing of genes take place
mostly by three methods-Conjugation, transformation & transduction.
GENETIC RESHUFFLING: It enables the production of traits that differ
from the original parent,
only the exogenote from the donor is transferred to recipient to enable
variation.
12. Comparative genomic analysis of closely related microorganisms that
exhibit different phenotypes have revealed distinct genomic differences.
Often, these idiosyncratic differences result from horizontal gene transfer ,
the movement genes that are not direct descendents from one another.
These horizontal gene transfers allows cells to quickly acquire new
characters and drives metabolic diversity.
Conjugation- transfer of genetic material occur through direct contact
between the two cells; donor and recipient
Transformation- The exogenate(portion of the genetic complement of the
donor) is taken up by the recipient from the surrounding medium,
Transduction- The transfer of a genetic materials occur from one cell to
other by bacteriophage or by a virus.
13.
14. The genome of the recipient is called endogenote and the incomplete
zygote is formed in this attribute is called partial diploid or merozygote.
Transfer of free DNA released from a donor bacterium to recipient
bacterium through the liquid medium in which they grow,
Does not require living bacteria cell, only requires DNA in the
environment,
Transfer DNA regions from 1-10 kilo bases of DNA,
A Kind of genetic transformation was discovered by F. Griffith (1928) on
the epoch making achievement. The experiment was conducted of the two
strains of Streptococcus pneumoniae (Pneumococcous pneumoniae) ; One
was virulent,(pathogenic) capsulated , smooth form(S) and other was
avirulent, non-pathogenic, non-virulent(non-pathogenic) rough(R).The
experiment designed as follows: Virulent strain(S) –injected into mice-mice
dead
Avirulent strain® –injected into mice-mice lives
Heat killed virulent(S)-injected into mice-mice lives
Heat killed virulent (S) + living virulent ®-injected into mice-mice dead.
Isolated S type strain from the dead mice from the last experiment .
15.
16. The Virulent and avirulent characters were nothing but the presence of
gene present there after.
The virulent strain responsible for the death of the mice but when it was
heated and injected, the effect of the gene did not produce any outcome.
But when the heat killed virulent strain treated with living avirulent, the
transformation of the avirulent to virulent one takes that caused the death
of the mice.
Initially, Griffith thought the virulence due to the polysaccharide present in
the capsule but later on, the experiment conducted by O. T. Avery, Mac
Leod & Mc Carty (1944) confirmed the transforming principle was none
but DNA, not polysaccharide present in the capsule. Thus research open a
new novel avenue of genetic research in the microbiological field.
Heat treated S+R=Mice death, Death mice- S type + R-type (Isolated
bacteria)
Dnase + heat treated S+R= Alive
Protease + heat treated S+ R= Death
17.
18. Competence is the process that enables the cell to incorporate the foreign
DNA,
The donor DNA binds to the cell surface by the DNA binding protein inside the
recipient cell,
Either dsDNA or ssDNA enters into the recipient cell,
The endonuclease enzyme degrades one of the strand and allows the
incorporation, ligase enzyme filled up the gap,
All bacteria in the medium containing donor DNA( exogenote) are not capable
of transformation, only the competent can have the pleasure of this
transformation. But the ability of transformation can be induced by certain
methods. On the basis of the ability of transformation, it can be divided into
two types
Natural transformation-Bacteria encoded with the competency factor in their
genome like mostly Gram(+) bacteria like S.pneumoniae, Bacillus subtilis etc,
Artificial Transformation-The artificial transformation can be induced in the
non-competent bacteria by the addition of cations like Ca or Rubidium chloride
or electroporation by heat shock in the medium like most Gram(-) negative
bacteria, Azetobacter agilus etc.
19. A kind of genetic transformation by which two sexually differentiated
bacterial cells –donor and recipient have the pleasure of it. A considerable
segment of donor genetic material is transferred to the recipient cells
which may undergo recombination with the corresponding (homologous)
segments of the recipient genetic materials. The segments of DNA may be
larger one in comparison to the other two methods of recombination.
According to Hayes( 1952), conjugation is a heterothallic system in which
recombination is mediated by one way transfer of genetic material from the
donor to recipient bacterial cell through the conjugation tube Let us explore
the beauty of this drama under two headings
Donor and Sex factor,
Process of conjugation & Sexduction.
20. Donor state is attributed by the presence of gene and it might be infectious
vector ( Hayes, 1953) in the donor cells. It is termed as Conjugons ( Luria,
1963) and conjugans termed as episomes.Episomes are cytoplasmic DNA
elements having capacity to integrate with the bacterial chromosome.
Donor state is called fertility factor or F factor like other factors Rtf, col
etc. When a bacterium contains F factor called F+ as male and the recipient
as F (-).F+ and Hfr are basically but the later can transfer large segments of
genome. Both F + and Hfr are characterized by the presence of flagellum
like structure on the cell surface called sex pilus. The sex factors perform
the following functions:
Determine the donor state, Help in the synthesis of surface antigen,
Mobilize the genetic material transfer
Provide enenergy during the process
21. F+ and F- Conjugation
This is the most normal when the F factor is transferred but not the
bacterial genome,
It converts the recipients to F+,
The circular dsDNA of the F factor is nicked on one of the strand,
The strand passes as a single strand into the recipient cell and synthesize
the complementary strand and circularizes into the recipient cell,
The donor dsDNA also regain the normal sate by following using
replication pattern,
The nick is made at the site called Ori T (origin of transfer) and the
replication occurs by rolling circle mechanisms.
22. Hfr and F- conjugation
Hfr is a strain where the F factor is integrated with the bacterial
chromosome. This integration is due to crossing over between the regions
of homology of shared by the plasmids and the bacterial genome. The
homologous sequence of DNA in the bacterial chromosome are called
insertion sequences.
When the Hfr strain comes in contact with F- strain, replication transfer
begins with F plasmid region at Ori T site and continues into the
chromosomal regions of the bacterial genome.
The transfer starts from the cut region and the bacterial DNA is transferred
through the conjugation tube keeping the F factor at its rear end,
If the entire DNA along with F factor is transferred , it becomes Hfr but
only bacterial genome transfers, it become F-
23.
24. The specific pairing occurs by the specific flagellum called sex pilus
present in both Hfr and F- cells which has a hole of 2.5µm diameter
through which the transfer of genetic material transfer takes place.
Recombination occurs only at homologous points
Specific pairing of the two strains are desired
Transfer of genetic material from donor to recipient,
Genetic recombination between donor and recipient cell,
Expression of new phenotype in the recipient cell is obligatory.
Transfer of plasmid DNA is efficient and rapid; under favorable conditions
virtually every recipient cells pairs with a donor acquires a plasmid.
Transfer of F plasmid having 100Kbp of DNA takes about 5 minutes.
25. It is a kind of conjugation between F`(Prime) and F- cells,
The male bacteria called F`, and F` cells have F factor with some genes of
the bacterial genome in it,
F` cells originate from Hfr strain. We know that Hfr is formed by the
integration with bacterial chromosome. But at times of integration reverts
during which the F factor brings some portion of the bacterial genome in
exchange of its own or even not. Thus the F factor has some genes of the
bacterial chromosome and becomes F`,
During conjugation between F` and F- cells, the F` factor is transferred to
the recipient F- cells. The recipient cell becomes a heterozygous for the
portion of genes present in the F` factor. Genetic recombination takes
place. The genetic recombination mediated by F` factor called sexduction
as identified by Adelberg and Burns (1956).
26. An unique type of genetic recombination where genes of one bacteria
transferred to another by means of bacteriophages, a vector. The virus of the
bacteriophage have the excitement of the transfer is called transducing phage.
This unique type of gene transfer was discovered by Zinder and Lederberg
(1952) on Salmonella typhimurium.
The overall process is as followed: Here, the bacteriophage acquires a portion
of bacterial DNA of the host cell where it reproduces and transfer it to the
another bacterial cell which it infects. Such phage is called transducing phage.
It is mediated by lambda phage that experiences Lysogenic type of life cycle,
The virus injects its nucleic acid into the host cell and the viral genomes
undergone integration with the bacterial genome and remain prophage for a
period of time during which it multiplies along with the reproduction of the
bacteria,
Delysogenisation occurs and viral genome detaches from the bacterial genome
to enter the lytic phase,
Viral genomes brings some bacterial genome may or may not exchange.
27.
28. The viral genome with some bacterial genes now included in new progeny
viruses which are released after lysis of the bacterial cell,
These bacteriophages with bacterial genes infect new bacterial cells in the
same manner and their genome gets integrated with the new host genome
and the genetic recombination occurs,
The second bacterial cells express some characters of the previous bacterial
cell by the courtesy of the virus, bacteriophage (lambda).
On the basis of the gene transfer as mediated bacteriophage, transduction
mainly of two types-
Generalized Transduction- Here the Lytic cycle is followed during
transduction.
Here, the bacterial DNA is disintegrated and the Lytic cycle is followed as
principle.
The virus instead of it own synthesized DNA, it collects bacterial DNA and
introduced to the another bacterial cell by Lytic process and integrates with
the new bacterial cell.
29. Specialized Transduction: This kind of genetic recombination is done by
the active participation of lysogeny cycle.
Here, the phage DNA is integrated with the bacterial DNA-called
prophage.
It attached with the bacterial until it becomes stable,
After unstable condition, it becomes get separated from the bacterial DNA ,
get separated from the host bacterial DNA along with its some of the
fragments of bacterial DNA,
Let, the viral genome collects ‘gal’ gene from the bacteria and inserted into
the another bacterial cell, insert the ‘gal’ gene into the second bacteria,
Now, the 2nd bacteria contains two ‘gal’ gene and get inserted into the
bacterial DNA. Now the new bacteria contains two ‘gal’ genes along with
the preexisting ‘bio’ gene.
As a result, the bacteria has been genetically modified by the virus via
transduction.
30.
31. When the lysate contains lower portion of ƛ dg it is called by LFT(Lower
Frequency of Transducing).When high proportion or all progeny
bacteriophages are ƛ dg, the lysate is called HFT (High Frequency of
Transducing).
Mobile DNA elements refers to discrete segments of DNA that moving as
units from one location to other within other DNA molecules. Most mobile
DNA elements that consists of transposable elements and the process by
this DNA movement takes place is called transposition. Two types of
transposable elements in Bacteria are Insertion sequences (IS) and
Transposons.They carry genes encoding transposase, the enzyme necessary
for transposition. These are two methods of the recombination in bacteria
are also fund beside the traditional genetic recombination found to occur in
this domain.
32. ACKNOWLEDGEMENT
Google for different images,
Different websites for content,
Introduction to Microbiology- Pelzer, Chan and Krieg,
Brook Biology of Microorganisms,
Microbiology & Phycology- Dash & Mishra,
A textbook of Microbiology- Dubey & Maheswari.
Disclaimer:
The content writer conveys thanks and acknowledges help from the following to
develop this article. This has been designed for online resources without any
financial interest.
