Structure of bacterial cell Surface structure 1 Capsule

Structure of bacterial cell Surface structure: 1 -Capsule 2 - Cells wall…. Peptidoglycan 3 - Cell membrane…. bilayer 4 - Appendages Flagella and Pili

Interior structure: o Cytoplasm (protoplast) o Gas vacuoles o Nutrients and enzymes o DNA o Ribosomes…. . 70 S o Mesosomes o Endospore (some)

Bacteria survival Endospore Spore formation usually occurs in rod-shaped bacteria (Bacillus and Clostridium). The formed spore may be located either: a) centrally , b) terminally c) sub-terminally.

Central endo-spore Terminal endo-spore Sub-terminal endo-spore

Features of endospore (Sporulation) 1 • Small spherical or oval bodies formed within the cell, due to the contraction of the cytoplasm. • It become surrounded by a thick wall and appear as glistening bodies. • It is capable of resisting unfavorable environmental conditions for many years.

Features of endospore (Sporulation) 2 • It can withstand boiling, desiccation and high concentrations of disinfectants. • When conditions become favorable, the spores germinate and are transformed into vegetative cells. • In some species the spore diameter is greater than the width of the bacterial cell.

The sporulation cycle of Bacillus subtilis.

The sporulation process is not one of multiplication , since most rod-shaped forms produce only one spore each. It is considered as a method for keeping the organism intact and surviving during un-favorable conditions.

Reproduction in Bacteria 1 - Binary fission 1. Binary fission: It occurs normally under favorable conditions. The cell elongates and becomes constricted at its middle. The cytoplasm divides and the constriction increases until the cell is split into two cells. The generation time (time needed for the cell to divide into two) differs according to species and prevailing conditions. The generation time ranges from 20 minutes to 6 hours under optimum conditions a single individual would produce several billions, a behavior which does not prevail due to the interference of other factors.

2 - Fragmentation (Conidia formation, exospores) It occurs in members of certain families belonging to Actionmycetes, e. g. Streptomyces. The ends of the filaments become septated and forming a chain of conidia similar to those produced by true fungi. These conidia can resist desiccation (similar to endospores) but they cannot resist high temperatures.