BACTERIAStructure, growth, nutrition &

classificationSOM302

N. B. Mannathoko

Mic

robi

olog

y

• ‘The study of living organisms which are too small to be viewedby the ‘unaided eye’ but visible with a microscope‘

• Range from tiny viruses to larger bacteria, protozoa, algae,fungi & some parasites

Rbc’s= 6-8m wide & 2m thickNeed ~140 rbc’s end-to-end to fill 1mm

E.coli

Red blood cell

• WHY STUDY THEM?

• Their pathogenicity,transmissibility & provocation of the immunesystem make them significant for the study of medicine

25 DEADLIESTdiseases in

human history

Cholera

Smallpox Yellow fever

TB

Influenza

LUNG CANCER

Diarrhoealdisease

PERINATALCOMPLICATIONS

WhoopingCough

Avianinfluenza

Tetanus

Chronic ObstructivePulmonary Disease

Ischemic HeartDisease

MeningitisInfluenza A-H1N1

(swine flu)

SyphilisLower

respiratoryinfections

CerebrovascularDisease

Bubonicplague

SARS

Leprosy

Measles

HIV

Malaria Caused by microorganisms

Monera

Classification of living organismsdomains & Kingdoms

Prokaryotic(pro-before; karyon-nucleus)

• Organelles absent except ribosomes

• DNA not enclosed in a membrane• Double-stranded• Single chromosome aggregated in cytoplasm• Haploid – single copy of each gene• Most bacteria have autonomous smaller circles

of DNA ‘plasmids’• Carry genes which confer special properties i.e. antibiotic

resistance

• Transcription coupled to translation incytoplasm

Eukaryotic(eu-true; karyon-nucleus)

Typically larger & more complex

• Several organelles e.g. ribosomes,mitochondria, chloroplasts

• DNA in a membrane enclosed nucleus• Double stranded with associated proteins• Packaged into linear chromosomes• Diploid – 2 copies of each gene• Several chromosome pairs e.g. bakers

years-16 pairs; human cells- 23 pairs

• Key processes in distinct areas:• DNA replication; transcription-nucleus• Protein synthesis/translation-cytoplasm

Archaea &Eubacteria

Archaea & Eubacteria• Single-celled

• No nucleus membrane• No organelles (except ribosomes)

Differences

Archaea• Extremophiles

(Extreme: temperatures, pH, salinity, high hydrostatic & osmotic pressures)

• Lipids, cell walls & flagella different to Eubacteria

• Not associated with human disease

• Some have significant role in gastrointestinal tract of ruminant animals

Eubacteria

Bacteria – Cellular Structure

DNA• Double-stranded• Tightly coiled into a region termed 'nucleoid’ - no nuclear membrane• Extrachromosomal DNA present as small circular DNA –’plasmids’

Cell envelope• Comprises the cytoplasmic membrane & cell wall

Capsules, flagella & pili variable-important role in diagnosis& pathogenicity)

Cytoplasm• Generally no organelles except

ribosomes (protein synthesis)

Ribosomes• Different structure in pro &

eukaryotic cells i.e. 50S & 30S inprokaryotes 60S & 40S ineukaryotes