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General Features of a Bacterial Cell

By

Dr.Jitender Kumar

Dept.Biotechnology

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Characteristic features of Bacteria

Bacteria are Prokaryotic organisms
Membrane bound cell organelle absent
DNA is a naked and single circular chromosome
No histones proteins are associated with DNA
Cell walls of peptidoglycan (polymer of NAG and NAM cross-linked with polypeptide chain)
Divide by binary fission

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Bacterial Cell

Typical bacteria cell

(Source: General microbiology by Stanier)

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Anatomy of bacterial cell

(Source:R.P.Singh)

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Genetic material of bacterial cell

Bacterial Chromosome in “nucleoid area”

(Source: General microbiology by Stanier)

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Genetics of bacterial cell

Bacterial chromosome and an extra-chromosomal “plasmid”

(Source: General microbiology by R.P.Singh)

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Prokaryotic Ribosomes

70s type of ribosomes are present

Smaller ribosome than eukaryotes

Involved in protein synthesis

Present in cytoplasm

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Binary Fission

Bacteria divide by “binary fission”

(Source:General microbiology by R.P.Singh)

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Types of Flagella

Flagella: complex organ of motility

A = monotrichous B = amphitrichous C = lophotrichous D = peritrichous

Source:General microbiology by R.P.Singh

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Bacterial Envelope

Bacterial “Envelope” – Structures on the outside of bacteria:
Glycocalyx – sugar coat, if tightly bound = capsule

Protects and prevents from drying, also protects from phagocytes
Slimy, and often a significant component of “biofilms”

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Structure of outer membrane of bacterial cell

Outer membrane (outside of cell wall) found in Gram (-) bacteria

(Source: General microbiology by R.P.Singh)

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Features of outer membrane

Outer membrane (outside of cell wall) found in Gram (-) bacteria
Gram – bacteria have LPS (lipopolysaccharide), lipoprotein, and phospholipids
These can cause some of the symptoms of Gram – bacterial infections (fever, shock, diarrhea)

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Cell Wall of bacterial cell

Bacterial Cell Wall – macromolecule, polysaccharide, repeating sugars, NAG and NAM, cross-linked with shot chains of Amino Acids
“Peptidoglycan, aka: murein”
Tough outer coat, prevents rupture, protects cell, gives it its distinct shape
Certain antibiotics work by inhibiting cell wall synthesis (penicillins)

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�Bacterial Cell Wall�

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Cell Wall

Source :R.P.Singh General microbiology

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Staining Method

Grams staining

Source :R.P.Singh General microbiology

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Shapes of bacteria

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Genetic basis of shape

Cell shape is determined by the genetic character of the organism. Its genes code for the synthesis of the CW material and the cell division mechanism that results in a “round” or “rod” or “spiral” shape.

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References

Source :R.P.Singh General microbiology
Source: General microbiology by Stanier)

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Thanks