Bacteria Structure, Growth And Taxonomy Flashcards
What are bacteria?
Unicellular ‘free living’ organisms;
Ancient but very successful;
Historically placed in kingdom Protista;
Monera (single cell)
Prokaryotes;
Unpaired chromosome;
No nucleus;
2 types - eubacteria and archaeobacteria;
Protests (single cell)
Eukaryotes;
Paired chromosomes;
Nuclear structure;
Protozoa and algae/ slime moulds;
Prokaryotes VS eukaryotes
Both have nucleic acids, ribosomes, cell membrane;
Eukaryotes have; prokaryotes don’t - structured nucleus, mitochondria, golgi, ER;
Prokaryotes have; eukaryotes don’t - Mesosome, rigid cell wall;
Bacteria nomenclature
Genus + Species;
Why is bacterial taxonomy important?
Handling information - facilitates storage and retrieval of info through use of databases;
Learning - facilitates learning and understanding large amounts of complex information about diverse organisms;
Communication - makes communication about bacteria more accurate;
Identification - makes identification of unknown bacteria possible;
Evolution - guide to evolution of bacteria - so epidemiological data is understood;
Classification of bacteria - phenotypic characteristics
Morphology - macroscopic, microscopic; Biotyping - biochemical tests; Serotyping; Antibiogram patterns; Pyocin/ phage typing;
Classification of bacteria - genotypic characteristics
% G+C ratios; DNA hybridisation; Nucleic acid sequence analysis; Chromosomal DNA fragment analysis; Ribotyping;
Macroscopic (growth on agar medium)
Shape;
Size;
Elevation;
Margin;
Texture - smooth/rough;
Appearance - glistening (shiny) or dull;
Pigmentation - nonpigmented (cream, Tan, white) or pigmented (purple, red, yellow);
Optical density (opaque/translucent);
Shapes
Rod; Club; Coccus (round); Curved (vibrio); Spirillum; Spirochaete;
Arrangement
Individual or groups/clusters/chains;
Staining characteristics of gram stain and acid fast chain
Gram chain - true bacteria;
Acid fast chain - mycobacteria
Shape of E. Coli
Short rod
Shape of Clostridium
Large club like rod;
Shape of Strep/staph
Coccus (round)
Staining characteristics - gram stain
Differentiates bacteria on the basis of cell wall structure;
Generally first line test in diagnosis of bacterial infections - gram result/size and shape of bacteria can be definitive for a particular genus of bacterium; empirical antibiotic treatment;
Gram positive - thick cell wall;
Gram negative - thin cell wall;
Gram positive example
Staphylococcus
Gram negative example
E. coli
Staph. Aureus is found in clusters or individually?
Clusters
E.coli is found in clusters or individually?
Individual
Cell envelope characteristics of gram negative VS gram positive
Gram positive - thicker cell wall, no outer membrane, has teichoic acid, has some strains of sporulation, sometimes has capsules, sensitive lysozyme, more susceptible to penicillin;
Gram negative - thinner cell wall, has outer membrane, no teichoic acid, no sporulation, sometimes has capsules, lysozyme not sensitive, less susceptible to penicillin;
Functions of the cell wall
Maintain rigidity and cell shape/structure - peptidoglycan (mesh like exoskeleton);
Maintain osmolarity - prevent osmotic lysis;
Survival - interacts with host cell membranes;
Cell division - forms cross-wall separation 2 Daughter cells;
Bacterial cell wall synthesis
Peptidoglycan precursor synthesized inside the cell;
Exported across cell membrane X bacitracin;
A site is created in existing wall by enzymic action (PBPs);
The new nucleotide minus the terminal D-ala is encorporated;
Cell grows;
Different cell wall morphologies - mycobacterium
Mycobacterium tuberculosis; Modified peptidoglycan layer; Covalently attached to arabinogalactan polymer; Mycolic acid waxy coat - lipids; Poor gram stain;
