The document discusses flagella, fimbriae, pili, and capsules in bacteria. It describes the structure and function of bacterial flagella, including their role in motility. It notes that flagella allow bacteria to move towards favorable environments or away from unfavorable ones. The document also discusses fimbriae and pili, describing them as hair-like structures that aid in adhesion and conjugation. Finally, it describes bacterial capsules as outer polysaccharide layers that protect cells and promote virulence by inhibiting phagocytosis.
A fimbria (Latin for 'fringe', plural fimbriae), also referred to as an "attachment pilus" by some scientists, is an appendage that can be found on many Gram-negative and some Gram-positive bacteria, that is thinner and shorter than a flagellum. This appendage ranges from 3–10 nanometers in diameter and can be up to several micrometers long. Fimbriae are used by bacteria to adhere to one another and to adhere to animal cells and some inanimate objects. A bacterium can have as many as 1,000 fimbriae. Fimbriae are only visible with the use of an electron microscope. They may be straight or flexible.
A pilus (Latin for 'hair'; plural: pili) is a hair-like appendage found on the surface of many bacteria and archaea.[1] The terms pilus and fimbria (Latin for 'fringe'; plural: fimbriae) can be used interchangeably, although some researchers reserve the term pilus for the appendage required for bacterial conjugation. All pili in the latter sense are primarily composed of pilin proteins, which are oligomeric.
FOLLOW US ON YOUTUBE # BIOTECH SIMPLIFIED #
Obligate intracellular, unable to self-replicate.
Once inside living cells, viruses induce the host cell to synthesize virus particles.
The genome is either DNA or RNA (single or double stranded).
Viruses do not have a system to produce ATP.
Viruses range in size from 25 to 270 nm.
Viral tropism!!
The classification of viruses is based on nucleic acid type, size and shape of virion, and presence or absence of an envelope.
Viral Structure
I . Virion is the entire viral particle.
2. Capsid is the protein coat that encloses the genetic material.
3. Capsomer is the protein subunit that makes up the capsid.
4. Nucleocapsid is composed of the capsid and genetic material.
5. The envelope is the outer coating composed of a phospholipid bilayer, which is composed of viral-encoded glycoproteins and sometimes viral encoded matrix proteins. The envelope is derived from a host cell's membrane.
Some viruses use the plasma membrane, whereas others use endoplasmic reticulum, Golgi, or nuclear membranes. Naked nucleocapsids are viruses with no envelopes.
A fimbria (Latin for 'fringe', plural fimbriae), also referred to as an "attachment pilus" by some scientists, is an appendage that can be found on many Gram-negative and some Gram-positive bacteria, that is thinner and shorter than a flagellum. This appendage ranges from 3–10 nanometers in diameter and can be up to several micrometers long. Fimbriae are used by bacteria to adhere to one another and to adhere to animal cells and some inanimate objects. A bacterium can have as many as 1,000 fimbriae. Fimbriae are only visible with the use of an electron microscope. They may be straight or flexible.
A pilus (Latin for 'hair'; plural: pili) is a hair-like appendage found on the surface of many bacteria and archaea.[1] The terms pilus and fimbria (Latin for 'fringe'; plural: fimbriae) can be used interchangeably, although some researchers reserve the term pilus for the appendage required for bacterial conjugation. All pili in the latter sense are primarily composed of pilin proteins, which are oligomeric.
FOLLOW US ON YOUTUBE # BIOTECH SIMPLIFIED #
Obligate intracellular, unable to self-replicate.
Once inside living cells, viruses induce the host cell to synthesize virus particles.
The genome is either DNA or RNA (single or double stranded).
Viruses do not have a system to produce ATP.
Viruses range in size from 25 to 270 nm.
Viral tropism!!
The classification of viruses is based on nucleic acid type, size and shape of virion, and presence or absence of an envelope.
Viral Structure
I . Virion is the entire viral particle.
2. Capsid is the protein coat that encloses the genetic material.
3. Capsomer is the protein subunit that makes up the capsid.
4. Nucleocapsid is composed of the capsid and genetic material.
5. The envelope is the outer coating composed of a phospholipid bilayer, which is composed of viral-encoded glycoproteins and sometimes viral encoded matrix proteins. The envelope is derived from a host cell's membrane.
Some viruses use the plasma membrane, whereas others use endoplasmic reticulum, Golgi, or nuclear membranes. Naked nucleocapsids are viruses with no envelopes.
Fungi is a group of eukaryotic non-phototropic organisms with rigid cell walls, that includes unicellular yeasts and multicellular molds. These slides will provide you the basics of fungi, general properties , reproduction and types of fungi.
Classifications of Fungi
Characteristics of all Fungi
Structure of Fungi
Reproduction
Classification of Fungi
Basidiomycota
sexual reproduction occur by basidium , will be present spore is called basidiospore .
Asexual by budding ,fragementation, conidiospores.
Ascomycota
microscopic sexual structure in which nonmotile spores, called ascospores.
Mostly the ascomycota is sexual but some asexual it lacks the ascospore.
Zygomycota
Two spore
mitospores ( or) sporangiospore
chlamitospore (or) zygospore
Deuteromycota
Imperfect Fungi referring to our "imperfect" knowledge of their complete life cycles.
sexual life cycle that is either unknown or absent.
Asexual reproduction is by means of conidia or may be lacking.
culture media
SDA medium – sabouraud dextrose agar
Algae are a diverse group of aquatic organisms that have the ability to conduct photosynthesis. Certain algae are familiar to most people; for instance, seaweeds (such as kelp or phytoplankton), pond scum or the algal blooms in lakes.
Fungi is a group of eukaryotic non-phototropic organisms with rigid cell walls, that includes unicellular yeasts and multicellular molds. These slides will provide you the basics of fungi, general properties , reproduction and types of fungi.
Classifications of Fungi
Characteristics of all Fungi
Structure of Fungi
Reproduction
Classification of Fungi
Basidiomycota
sexual reproduction occur by basidium , will be present spore is called basidiospore .
Asexual by budding ,fragementation, conidiospores.
Ascomycota
microscopic sexual structure in which nonmotile spores, called ascospores.
Mostly the ascomycota is sexual but some asexual it lacks the ascospore.
Zygomycota
Two spore
mitospores ( or) sporangiospore
chlamitospore (or) zygospore
Deuteromycota
Imperfect Fungi referring to our "imperfect" knowledge of their complete life cycles.
sexual life cycle that is either unknown or absent.
Asexual reproduction is by means of conidia or may be lacking.
culture media
SDA medium – sabouraud dextrose agar
Algae are a diverse group of aquatic organisms that have the ability to conduct photosynthesis. Certain algae are familiar to most people; for instance, seaweeds (such as kelp or phytoplankton), pond scum or the algal blooms in lakes.
Bacteria are a type of biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. Bacteria were among the first life forms to appear on Earth, and are present in most of its habitats
What is bacteria?(Structures Present in Bacteria And their Functions | Prokar...sehriqayyum
Explains what bacteria is and where it exists.
A key feature of nearly all prokaryotic cells is the cell wall, which maintains cell shape, protects the cell, and prevents it from bursting in a hypotonic environment.
The cell walls of prokaryotes differ in structure from those of eukaryotes. In eukaryotes that have cell walls, such as plants and fungi, the walls are usually made of cellulose or chitin. In contrast, most bacterial cell walls contain peptidoglycan, a polymer composed of modified sugars cross-linked by short polypeptides.
Using a technique called the Gram stain, developed by the 19th-century Danish physician Hans Christian Gram, scientists can categorize many bacterial species according to differences in cell wall composition.
Gram-positive bacteria have simpler walls with a relatively large amount of peptidoglycan. Gram-negative bacteria have less peptidoglycan
and are structurally more complex, with an outer membrane
that contains lipopolysaccharides (carbohydrates bonded
to lipids).
LEARN ABOUT:
- Bacteria
- The number of viruses on earth is staggering
- Pathogenic yeasts
- Helminths
- Harnessing bacteria
- Microbes on the tree of life
- Living and working together
- Archaea
- Protozoa
LEARN ABOUT:
- Bacteria
- The number of viruses on earth is staggering
- Pathogenic yeasts
- Helminths
- Harnessing bacteria
- Microbes on the tree of life
- Living and working together
- Archaea
- Protozoa
The bacterial flagellum has three main parts (the motor, hook, and filament) that are themselves composed of 42 different kinds of proteins.The cells of prokaryotes are simpler than those of eukaryotes
in both their internal structure and the physical arrangement
of their DNA. The genome of a prokaryote is structurally different from
a eukaryotic genome and in most cases has considerably less DNA. Prokaryotes generally have circular chromosomes, whereas eukaryotes have linear chromosomes.
Bacteria are unicellular, procaryotic microorganisms which have diverse shape size and structures. Bacteria are found almost everywhere on Earth. Even the human body is full of bacteria, and in fact is estimated to contain more bacterial cells than human cells. Most bacteria in the body are harmless, and some are even helpful. A relatively small number of species cause disease.
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 ability to recreate computational results with minimal effort and actionable metrics provides a solid foundation for scientific research and software development. When people can replicate an analysis at the touch of a button using open-source software, open data, and methods to assess and compare proposals, it significantly eases verification of results, engagement with a diverse range of contributors, and progress. However, we have yet to fully achieve this; there are still many sociotechnical frictions.
Inspired by David Donoho's vision, this talk aims to revisit the three crucial pillars of frictionless reproducibility (data sharing, code sharing, and competitive challenges) with the perspective of deep software variability.
Our observation is that multiple layers — hardware, operating systems, third-party libraries, software versions, input data, compile-time options, and parameters — are subject to variability that exacerbates frictions but is also essential for achieving robust, generalizable results and fostering innovation. I will first review the literature, providing evidence of how the complex variability interactions across these layers affect qualitative and quantitative software properties, thereby complicating the reproduction and replication of scientific studies in various fields.
I will then present some software engineering and AI techniques that can support the strategic exploration of variability spaces. These include the use of abstractions and models (e.g., feature models), sampling strategies (e.g., uniform, random), cost-effective measurements (e.g., incremental build of software configurations), and dimensionality reduction methods (e.g., transfer learning, feature selection, software debloating).
I will finally argue that deep variability is both the problem and solution of frictionless reproducibility, calling the software science community to develop new methods and tools to manage variability and foster reproducibility in software systems.
Exposé invité Journées Nationales du GDR GPL 2024
Toxic effects of heavy metals : Lead and Arsenicsanjana502982
Heavy metals are naturally occuring metallic chemical elements that have relatively high density, and are toxic at even low concentrations. All toxic metals are termed as heavy metals irrespective of their atomic mass and density, eg. arsenic, lead, mercury, cadmium, thallium, chromium, etc.
Slide 1: Title Slide
Extrachromosomal Inheritance
Slide 2: Introduction to Extrachromosomal Inheritance
Definition: Extrachromosomal inheritance refers to the transmission of genetic material that is not found within the nucleus.
Key Components: Involves genes located in mitochondria, chloroplasts, and plasmids.
Slide 3: Mitochondrial Inheritance
Mitochondria: Organelles responsible for energy production.
Mitochondrial DNA (mtDNA): Circular DNA molecule found in mitochondria.
Inheritance Pattern: Maternally inherited, meaning it is passed from mothers to all their offspring.
Diseases: Examples include Leber’s hereditary optic neuropathy (LHON) and mitochondrial myopathy.
Slide 4: Chloroplast Inheritance
Chloroplasts: Organelles responsible for photosynthesis in plants.
Chloroplast DNA (cpDNA): Circular DNA molecule found in chloroplasts.
Inheritance Pattern: Often maternally inherited in most plants, but can vary in some species.
Examples: Variegation in plants, where leaf color patterns are determined by chloroplast DNA.
Slide 5: Plasmid Inheritance
Plasmids: Small, circular DNA molecules found in bacteria and some eukaryotes.
Features: Can carry antibiotic resistance genes and can be transferred between cells through processes like conjugation.
Significance: Important in biotechnology for gene cloning and genetic engineering.
Slide 6: Mechanisms of Extrachromosomal Inheritance
Non-Mendelian Patterns: Do not follow Mendel’s laws of inheritance.
Cytoplasmic Segregation: During cell division, organelles like mitochondria and chloroplasts are randomly distributed to daughter cells.
Heteroplasmy: Presence of more than one type of organellar genome within a cell, leading to variation in expression.
Slide 7: Examples of Extrachromosomal Inheritance
Four O’clock Plant (Mirabilis jalapa): Shows variegated leaves due to different cpDNA in leaf cells.
Petite Mutants in Yeast: Result from mutations in mitochondrial DNA affecting respiration.
Slide 8: Importance of Extrachromosomal Inheritance
Evolution: Provides insight into the evolution of eukaryotic cells.
Medicine: Understanding mitochondrial inheritance helps in diagnosing and treating mitochondrial diseases.
Agriculture: Chloroplast inheritance can be used in plant breeding and genetic modification.
Slide 9: Recent Research and Advances
Gene Editing: Techniques like CRISPR-Cas9 are being used to edit mitochondrial and chloroplast DNA.
Therapies: Development of mitochondrial replacement therapy (MRT) for preventing mitochondrial diseases.
Slide 10: Conclusion
Summary: Extrachromosomal inheritance involves the transmission of genetic material outside the nucleus and plays a crucial role in genetics, medicine, and biotechnology.
Future Directions: Continued research and technological advancements hold promise for new treatments and applications.
Slide 11: Questions and Discussion
Invite Audience: Open the floor for any questions or further discussion on the topic.
Deep Behavioral Phenotyping in Systems Neuroscience for Functional Atlasing a...Ana Luísa Pinho
Functional Magnetic Resonance Imaging (fMRI) provides means to characterize brain activations in response to behavior. However, cognitive neuroscience has been limited to group-level effects referring to the performance of specific tasks. To obtain the functional profile of elementary cognitive mechanisms, the combination of brain responses to many tasks is required. Yet, to date, both structural atlases and parcellation-based activations do not fully account for cognitive function and still present several limitations. Further, they do not adapt overall to individual characteristics. In this talk, I will give an account of deep-behavioral phenotyping strategies, namely data-driven methods in large task-fMRI datasets, to optimize functional brain-data collection and improve inference of effects-of-interest related to mental processes. Key to this approach is the employment of fast multi-functional paradigms rich on features that can be well parametrized and, consequently, facilitate the creation of psycho-physiological constructs to be modelled with imaging data. Particular emphasis will be given to music stimuli when studying high-order cognitive mechanisms, due to their ecological nature and quality to enable complex behavior compounded by discrete entities. I will also discuss how deep-behavioral phenotyping and individualized models applied to neuroimaging data can better account for the subject-specific organization of domain-general cognitive systems in the human brain. Finally, the accumulation of functional brain signatures brings the possibility to clarify relationships among tasks and create a univocal link between brain systems and mental functions through: (1) the development of ontologies proposing an organization of cognitive processes; and (2) brain-network taxonomies describing functional specialization. To this end, tools to improve commensurability in cognitive science are necessary, such as public repositories, ontology-based platforms and automated meta-analysis tools. I will thus discuss some brain-atlasing resources currently under development, and their applicability in cognitive as well as clinical neuroscience.
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.
(May 29th, 2024) Advancements in Intravital Microscopy- Insights for Preclini...Scintica Instrumentation
Intravital microscopy (IVM) is a powerful tool utilized to study cellular behavior over time and space in vivo. Much of our understanding of cell biology has been accomplished using various in vitro and ex vivo methods; however, these studies do not necessarily reflect the natural dynamics of biological processes. Unlike traditional cell culture or fixed tissue imaging, IVM allows for the ultra-fast high-resolution imaging of cellular processes over time and space and were studied in its natural environment. Real-time visualization of biological processes in the context of an intact organism helps maintain physiological relevance and provide insights into the progression of disease, response to treatments or developmental processes.
In this webinar we give an overview of advanced applications of the IVM system in preclinical research. IVIM technology is a provider of all-in-one intravital microscopy systems and solutions optimized for in vivo imaging of live animal models at sub-micron resolution. The system’s unique features and user-friendly software enables researchers to probe fast dynamic biological processes such as immune cell tracking, cell-cell interaction as well as vascularization and tumor metastasis with exceptional detail. This webinar will also give an overview of IVM being utilized in drug development, offering a view into the intricate interaction between drugs/nanoparticles and tissues in vivo and allows for the evaluation of therapeutic intervention in a variety of tissues and organs. This interdisciplinary collaboration continues to drive the advancements of novel therapeutic strategies.
3. FLAGELLA
• Some bacteria are motile and some are not. Almost all motile
bacteria possess flagella as the organ of locomotion.
• Such bacteria tend to move towards or away from the source of
stimulus. These stimuli can be chemicals (chemotaxis), light
(phototaxis), air (aerotaxis) or magnetism (magnetotaxis).
4. Structure of Flagella:
• Prokaryotic flagella are much thinner than eukaryotic flagella and
they lack the typical 9 + 2 arrangement of microtubules.
• Over 40 genes are involved in its assembly and function.
• They are approximately 3-20µm long and end in a square tip.
• Since flagella are very thin (20-30 nm in diameter), they are below the
resolution limits of a normal light microscope and cannot be seen.
5. • The bacterial flagellum is a non contractile, composed of single kind of protein subunit called
flagellin.
• It is anchored to the bacterial cytoplasmic membrane and cell well by means of disklike structures.
• A flagellum comprises of three parts, filament, hook and basal body.
• The flagellum is attached to the cell body by hook and basal body. While the hook and basal body
are embedded in the cell envelope, the filament is free.
• If a flagellum is cut off it will regenerate until reaches a maximum length. This is so because the
growth is not from base, but from tip.
• The basal body bears a set of rings, one pair in gram positive bacteria and two pairs in gram
negative bacteria. While the rings named S and M are common to both, the rings names P and L
are found only in gram negative bacteria.
6. • Rings in the basal body rotate relative to each other causing the flagella to turn
like a propeller.
• The energy to drive the basal body is obtained from the proton motive force.
• Bacteria move at average speed of 50µm/sec, the fastest being Vibrio cholerae that
moves 200µm/sec.
• The numbers of flagella, as well as their location on the cell surface are
characteristic of a species.
7. Flagella arrangements are:
1. Monotrichous - a single flagellum at one pole (also called polar
flagellum) E.g. Vibrio cholerae
2. Amphitrichous - single flagellum at both poles. Eg. Spirilla
3. Lophotrichous - two or more flagella at one or both poles of the cell
E.g. Spirillum undula
4. Peritrichous - completely surrounded by flagella E.g. E.coli
8.
9. • Other mechanisms of bacterial locomotion include gliding and motion
by axial filament contraction.
• Gliding is movement of bacteria along solid surfaces by an unknown
mechanism.
• Spirochetes have internally-located axial filaments or endo flagella.
Axial filaments wrap around the spirochete towards the middle from
both ends.
• They are located above the peptidoglycan cell wall but below the outer
membrane.
10. Detection bacterial motility:
1) Direct observation by means of hanging drop preparation
2) Special-purpose microscopes (phase-contrast and dark-field)
3) Motility media (semi solid agar)
4) Indirectly, by demonstration of flagella
Flagella staining (Silver impregnation, Leifson’s method)
Electron microscopy
Immunological detection of flagellar “H” antigen
11. Types of bacterial motility:
• Stately motility: Bacillus sps
• Active motility: Pseudomonas sps
• Darting motility: Vibrio cholerae
• Tumbling motility: Listeria monocytogens
• Corkscrew, extension-flexion motility: Spirochetes
Examples of non-motile bacteria: Most cocci, Shigella, Klebsiella
12. FUNCTION OF FLAGELLA:
• Flagella helps in moment of bacterial cell
• Flagella also help in attachment with other cell
• Also help in Asexual reproduction
• Help in conjugation
• Flagella attached with human cell which used as pathogencity , which caused
infection
• Flagella act as Virulence
• Primarily function is motility (chemotaxis, aerotaxis, phototaxis etc). Positive taxis
is movement toward a favorable environment whereas negative taxis is movement
away from a repellent.
• Flagella can help in identifying certain types of bacteria. For example, Proteus
species show ‘swarming’ type of growth on solid media.
• Flagellar antigens are used to distinguish different species and strains of bacteria
(serovars). Variations in the flagellar H antigen are used in serotyping.
14. FIMBRIAE AND PILI
• Fimbriae are short, hair-like structures made up of protein pilin and are present in
many gram negative bacteria.
• Even though pili arise from plasma membrane they are not considered part of the
plasma membrane.
• They are anchored in the membrane and protrude through the cell wall to the outside
of the cell.
• Fimbriae are shorter and straighter than flagella and are more numerous. They are
0.5µm long and 10 nm thick. Since they are made up of protein, they are antigenic.
• Bacteria from different genera may possess common fimbrial antigens.
• Fimbriae are usually seen in young cultures and lost on subcultures on solid media.
While some authors use the two terms (fimbriae and pili) interchangeably, some
restrict the term pili to denote sex pili.
• Sex pili acts to join bacterial cells for transfer of DNA from one cell to another by a
process called conjugation.
15. TYPES OF PILLI:
• Have two types
1) Conjugative pilli
2) Type IV pill
16. 1) Conjugative pili
• Conjugative pili allow for the transfer of DNA between bacteria, in the
process of bacterial conjugation.
• They are sometimes called "sex pili", in analogy to sexual
reproduction, because they allow for the exchange of genes via the
formation of "mating pairs".
• Perhaps the most well-studied is the F pilus of Escherichia coli,
encoded by the F plasmid or fertility factor.
17. • A pilus is typically 6 to 7 nm in diameter. During conjugation, a pilus emerging from the
donor bacterium ensnares the recipient bacterium, draws it in close, and eventually
triggers the formation of a mating bridge, which establishes direct contact and the
formation of a controlled pore that allows transfer of DNA from the donor to the
recipient.
• Typically, the DNA transferred consists of the genes required to make and transfer pili
(often encoded on a plasmid), and so is a kind of selfish DNA; however, other pieces of
DNA are often co-transferred and this can result in dissemination of genetic traits
throughout a bacterial population, such as antibiotic resistance. Not all bacteria can make
conjugative pili, but conjugation can occur between bacteria of different species
18. 2) Type IV pili:
• Some pili, called type IV pili, generate motile forces.
• The external ends of the pili adhere to a solid substrate, either the
surface to which the bacteria are attached or to other bacteria, and
when the pilus contracts, it pulls the bacteria forward, like a grappling
hook.
• Movement produced by type IV pili is typically jerky, and so it is
called twitching motility, as distinct from other forms of bacterial
motility, such as motility produced by flagella.
• However, some bacteria, for example Myxococcus xanthus, exhibit
gliding motility.
• Bacterial type IV pilins are similar in structure to the component
flagellins of Archaeal flagella.
19. Demonstration of fimbriae:
• Electron microscopy
• Haemagglutination
• Immunological detection of fimbrial antigen
20. Function of Pili:
Pili connect a bacterium to another of its species, or to another bacterium of
a different species, and build a bridge between the interior of the cells. This enables
the transfer of plasmids between the bacteria. An exchanged plasmid can code for
new functions, e.g., antibiotic resistance.
• Filamentous appendages up to 30 µm long and 20-30nm thick
• Self assembly
• Adhesion to surfaces
• Sex pili involved in conjugation
21. • They act as adhesins and allow bacteria to colonize cells. For example, Neisseria gonorrhoea
uses its fimbriae to attach to the lining of the genital tract and initiate an infection.
• Fimbriae can also detect chemical signals and are important in bacterial cell communication
and biofilm formation.
• Fimbriae also act as receptors for bacteriophages.
• Fimbriae of Streptococcus pyogenes are coated with M protein, which acts as an important
virulence factor by adhering to host cells and resisting phagocytosis.
• Fimbriated bacteria form surface pellicle of liquid media.
• Some fimbriae can agglutinate RBC of guinea pigs, horses, pigs and fowls. This
haemagglutination may or may not be inhibited by mannose.
23. Capsules:
The bacterial capsule is a layer of material, usually polysaccharide,
attached to the cell wall possibly via covalent attachments to either
phospholipid or lipid-A molecules.
24. • External layer of polysaccharide (except B antracis Dglutamic acid
polymer)
• C/N nutrition dependent
• Homo or hetero polysaccharide (usually amino hexoses)
• Serves to protect cells eg phagocytosis, dessication etc.
• Outer layer
• Polysaccharide usually (sometimes polypeptide)
• Unstructured : loose association
• Promotes virulence in pathogenic (diseasecausing) bacteria
• Inhibits phagocytosis by leucocytes
• Streptococcus pneumoniae.
• Bacillus anthracis
Cap+ virulent
Cap- non-virulent