28 Bacterial GenomeMost bacteria contain a single circular double strand of DNA called a nucleoid.
29 Prokaryotic RibosomeA ribosome is a combination of RNA and protein, and is the site for protein synthesisComposed of large (50S) and small (30S) subunitsS = Svedverg unit, measures molecular size
30 Inclusion BodiesInclusion bodies enable a cell to store nutrients and to survive in nutrient depleted environments
31 Bacterial Cytoskeleton Actin is a protein fiber present in some bacteria, which is involved in maintaining cell shape.
32 EndosporesNutrient depletion induces some bacteria (vegetative cell) to form endospores in order to surviveDehydrated gel state due to calcium-protein complexDipicolinic acid (found only in spores) hardens the spore
33 Endospore FormationSome pathogenic bacteria that produce toxins during the vegetative stage are capable of forming spores. (e.g. Bacillus and Clostridium species)
34 Bacterial Morphology Coccus Rod or bacillus Curved or spiral Cell arrangementsPleomorphism
35 Typical Shapes and Arrangements Scanning electron micrographs of different bacterial shapes and arrangements.(a) Streptococcus (b) Bacillus (c) Spirochete (d) Spirillum
36 PleomorphismSome bacteria show varied shapes and arrangements called pleomorphism. Ex: Corynebacterium diphtheriae’s “Chinese letter” arrangement.
37 Bacterial Shapes and Arrangements Cellular shapes and arrangements are useful in bacterial identification.
38 The Dimension of Bacteria Relative size of a bacterial cell compared to other cells including viruses.
39 Classification Phenotypic methods Molecular methods Taxonomic scheme Unique groups
40 Phenotypic Methods Cell morphology - staining Biochemical test – enzyme test
42 Major Taxonomic Groups of Bacteria The methods of classification have allowed bacteria to be classified into different taxonomic groupsRe: Bergey’s Manual of Determinative Bacteriology(Table on right)