Sporulation is the process of spores formation by bacteria during unfavorable condition
Germination is the process of spores return to give vegetative cells under favorable condition.
Bacteria are microscopic, single-celled organisms that thrive in diverse environments. These organisms can live in soil, the ocean and inside the human gut. Humans' relationship with bacteria is complex. Sometimes bacteria lend us a helping hand, such as by curdling milk into yogurt or helping with our digestion.
Pure Culture Technique
Culture : Act of cultivating microorganisms or the microorganisms that are cultivated.
Mixed culture : more than one microorganism
Pure culture : containing a single species of organism.
Common isolation techniques:
1. Streak plate method
2. Pour plate method
3. Spread plate method
4. Roll tube method
Bacteria are microscopic, single-celled organisms that thrive in diverse environments. These organisms can live in soil, the ocean and inside the human gut. Humans' relationship with bacteria is complex. Sometimes bacteria lend us a helping hand, such as by curdling milk into yogurt or helping with our digestion.
Pure Culture Technique
Culture : Act of cultivating microorganisms or the microorganisms that are cultivated.
Mixed culture : more than one microorganism
Pure culture : containing a single species of organism.
Common isolation techniques:
1. Streak plate method
2. Pour plate method
3. Spread plate method
4. Roll tube method
Direct methods of measurement of microbial growth includes various methods of enumeration of both viable and non viable cell also includes growth curve. Helpful for UG and PG programs of microbiology
When fresh liquid medium is inoculated with a given number of bacteria and incubated for sufficient period of time, it gives a characteristic growth pattern of bacteria.
If the bacterial population is measured periodically and log of number of viable bacteria is plotted in a graph against time, it gives a characteristic growth curve which is known as growth curve or growth cycle.
Growth of bacteria is affected by many factors such as nutrition concentration and other environmental factors.
Some of the important factors affecting bacterial growth are:
Nutrition concentration
Temperature
Gaseous concentration
pH
Ions and salt concentration
Available water
GROWTH OF BACTERIA CANNOT BE MEASURED DIRECTLY BY SEEING THEM AS THEY ARE MICROSCOPIC STRUCTURES THEREFORE WE HAVE TO USE SEVERAL METHODS WHICH ARE DESCRIBED IN THIS PRESENTATION
Ultrastructure and characterstic features of bacteria.Archana Shaw
Ultrastructure and characterstic features of bacteria: BACTERIA AS A MODEL ORGANISM
THIS WAS MY PRESENTATION TOPIC IN CLASS. THOUGHT OF SHARING IT AND HOPE IT HELPS.
The physical factors affects the growth of microorganism.
1) Temperature
Temperature is the most important factor that influences the rate of enzyme catalysed reactions and rate of growth.
For every organisms there is an optimum temperature for growth and minimum temperature for inhibiting the growth.
Most extreme the microbes need liquid water to grow.(330C).
some algae and fungi grow at 55-60 degreeC.
Prokaryotes are grow at 100 degreeC.
Based on temperature the microorganisms are classified into two 4.
Direct methods of measurement of microbial growth includes various methods of enumeration of both viable and non viable cell also includes growth curve. Helpful for UG and PG programs of microbiology
When fresh liquid medium is inoculated with a given number of bacteria and incubated for sufficient period of time, it gives a characteristic growth pattern of bacteria.
If the bacterial population is measured periodically and log of number of viable bacteria is plotted in a graph against time, it gives a characteristic growth curve which is known as growth curve or growth cycle.
Growth of bacteria is affected by many factors such as nutrition concentration and other environmental factors.
Some of the important factors affecting bacterial growth are:
Nutrition concentration
Temperature
Gaseous concentration
pH
Ions and salt concentration
Available water
GROWTH OF BACTERIA CANNOT BE MEASURED DIRECTLY BY SEEING THEM AS THEY ARE MICROSCOPIC STRUCTURES THEREFORE WE HAVE TO USE SEVERAL METHODS WHICH ARE DESCRIBED IN THIS PRESENTATION
Ultrastructure and characterstic features of bacteria.Archana Shaw
Ultrastructure and characterstic features of bacteria: BACTERIA AS A MODEL ORGANISM
THIS WAS MY PRESENTATION TOPIC IN CLASS. THOUGHT OF SHARING IT AND HOPE IT HELPS.
The physical factors affects the growth of microorganism.
1) Temperature
Temperature is the most important factor that influences the rate of enzyme catalysed reactions and rate of growth.
For every organisms there is an optimum temperature for growth and minimum temperature for inhibiting the growth.
Most extreme the microbes need liquid water to grow.(330C).
some algae and fungi grow at 55-60 degreeC.
Prokaryotes are grow at 100 degreeC.
Based on temperature the microorganisms are classified into two 4.
Living material is organized in unit and microorganism were living form of microscopical size and usually unicellular in structure originally classification is unsatisfied.
Professional air quality monitoring systems provide immediate, on-site data for analysis, compliance, and decision-making.
Monitor common gases, weather parameters, particulates.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
A brief information about the SCOP protein database used in bioinformatics.
The Structural Classification of Proteins (SCOP) database is a comprehensive and authoritative resource for the structural and evolutionary relationships of proteins. It provides a detailed and curated classification of protein structures, grouping them into families, superfamilies, and folds based on their structural and sequence similarities.
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
2. • What is bacterial spore.
• Why was bacterium tend to convert into spore.
• What is spore structure.
• Shape and location of endospore.
• Mechanism of sporulation and germination.
• Medical Importance of Bacterial Spores.
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3. • Bacteria have two phases life cycle:
Vegetative cell – Metabolically active and growth.
Bacterial spore - metabolically dormant structure, high resistance to
sever conditions and very long-term survival, reach to millions of years.
• Sporulation is the process of spores formation by bacteria during
unfavorable condition
• Germination is the process of spores return to give vegetative
cells under favorable condition.
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4. • Endospore is a dormant, tough, and non-reproductive
structure produced by some bacteria in the phylum
Firmicutes like Bacillus and Clostridium when exposed to
sever environmental conditions like nutrition starvation.
• An endospore is:
Hardiest of all life form.
Resistance to heat, drying, freezing, radiation, extreme pH,
antibiotics and chemicals.
Not a mean of reproduction.
Destroys by pressured steam at 120oC for 20-30 minutes.
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6. 15 June 2022
An endospore has following layers:
1. Exosporium 2. Spore coat 3. Cortex 4. core
Exosporium: is the outer layer made up of protein that encloses spore coat. In some bacterial spore, exosporium is
made up of polysaccharide and lipid.
Spore coat: is thick double layered that encloses cortex. Spore coat consists of specific protein, mainly contains
cysteine and hydrophobic amino acids. Due to presence of these amino acids, spore is resistant to
adverse environmental condition.
Cortex: is made up of loosely arranged peptidoglycan layer. it can be hydrolyzed during spore germination.
Core: is the inner part of spore contains (10-25%) water so, the cytoplasm is gel like. It consists of core wall,
cytoplasmic membrane, cytoplasm, nucleic acid, ribosomes and other cellular materials. It contains high
amount of calcium and Dipicolinic acid which play a role in the heat resistance of bacterial endospores . Core
also contains high percentage of small acid soluble protein (SASP), which is synthesized during sporulation
and it binds to DNA in core and protect it from potential damage caused by UV radiation and drying. In
addition, SASPs also provides nutrition and energy for spore germination.
7. • The shape and location of bacterial spore are characteristic of
the different sporulating strains and can be used as
distinguishing features.
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1 4 5 6 7
3
2
1. Terminal spherical endospore
2. Sub-terminal spherical endospore
3. central spherical endospore.
4. Terminal oval endospore
5. Sub-terminal oval endospore
6. central oval endospore
7. lateral endospore
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Clostridium tetani with
terminal spherical endospore
(drum-stick-shape)
Clostridium botulinum
with Sub-terminal oval
endospore
clostridium perfringens
with Sub-terminal oval
endospore
Bacillus spp. In chain
with central spherical
endospore
9. 15 June 2022
• During unfavorable condition, vegetative cell converts into spore. The one
vegetative cell forms a single spore. It takes 8 to19 hrs to complete.
• Sporulation can be divided into several stages.
1. Stage 0: Normal conditions of a vegetative cell
2. Stage I: Axial filament formation stage
• In this stage bacterial chromosome become thread like known as axial filament.
• Axial filaments attached to cytoplasmic membrane by mesosome.
• Elongation of cell take places.
3. Stage II: forespore formation
• Asymmetric cell division occurs.
• Cell membrane forms septum near one end which encloses a small portion of DNA
forming forespore.
10. 15 June 2022
4. Stage III: engulfment of forespore.
• Mother cell membrane grow around the forespore engulfing it.
• Forespore now has two membrane layer.
5. Stage IV: synthesis of exosporium.
• Chromosome of mother cell disintegrates.
• Forespore starts forming primodial cortex between two membranes.
• Dehydration of cell.
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6. Stage V: synthesis of dipicolinic acid
• Production of SASPs and dipicolinic acid occurs.
• Incorporation of calcium ions with dipicolonic acid occur forming
calcium dipicolinate.
• Further dehydration of cytoplasm.
• Formation of coat layer
7. Stage VI: maturation
• Maturation of endospore
8. Stage VII: release of endospore
• Cell lysis and release of endospore
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• Endospore remains dormant for years. But under favorable conditions
each endospore germinates to give one vegetative cell.
• Spore germination involves 3 process.
A. Activation of endospore: The germination of bacterial spore does not
occur even when the environment is favorable unless it is first activated. At
first the spore coat must be damaged by heating for several minutes.
B. Germination: The activated spore initiates germination after binding of
effector molecules. Binding of effectors molecules activates autolysis that
destroy peptidoglycan of cortex. After destruction of peptidoglycan, water is
taken up and calcium dipicolinic acid is released.
C. Outgrowth: After uptake of water swelling of spore occurs along with the
synthesis of DNA, RNA and proteins. A small germ cell emerges out after
breaking the spore coat and begins to grow into vegetative cell.
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Important features of Spores Medical Implications
Spores are highly resistant to heating; spores
are not killed by boiling (100°C) but are killed
at 121°C.
Medical supplies must be heated to 121°C for at
least 15 minutes to be sterilized.
Spores are highly resistant to many
chemicals, including most disinfectants.
Only solution designated as sporicidal will kill
spores.
Spores can survive for many years in soil and
other inanimate objects.
Wound contaminated with soils can be infected
with spores and cause diseases such as tetanus,
gas gangrene.
Spores do not exhibit measurable metabolic
activity.
Antibiotics are ineffective against spores.
Spores formed only when nutrients are
insufficient.
Spores are not often found at the site of
infection because nutrients are not limiting.
