Bacterial pathogens I

Microorganisms are classified as

prokaryotes or eukaryotic protists

Eukaryotic protists are

fungi, mould, protoza

what drives ATP production in prokaryotes

Proton Motive Force

Where are terrestrial habitats found

part in soil formation and essential for ecosystem

Where are aquatic bacteria found

fresh/salt water

where are animals bacteria found

Microbiomes

Where are bacteria found in extreme environments

hot springs/ snow

Genotypic identification uses

DNA + RNA homology

Phenotypic identification uses

staining, biochemical and antigen and antibody

Medical Microbiology

Study of small no. Of pathogenic and potentially pathogenic bacteria that causes disease

Obligated aerobes

Require oxygen

Obligate anaerobes

Don’t require oxygen

Facultative aerobes

Grows with or without oxygen as it has other paths for energy

Microaerophilic aerobe

Oxygen but a reduced level

Nutrionally complex/fastidious

Require complex nutrients

Positive gram cells

Retains dye crystal after alcohol/acetone

+ve gram cells have what colour

Purple

-ve gram cells

Take up a counterstain

-ve gram cells colour

Red

Why dont mycobacterium/Nocardia take up aniline dyes

High content cell wall lipids

First step of acid fast stain

Red dye phenol first applied

2nd step of acid fast stain

Methyline blue e.g used as a counterstain (non acid fast stain)

What size are bacteria

0.1 - 20 microm

Diameter of a bacteria

0.2 - 2 microm

Coccus bacteria

Spherical shaped and occurs in clusters

Bacilli

Rod shaped that are long square or short round

Vibrio

Curved bacteria with a single turn

Spirillium/spirochete

Spiral organisms with a series of turns

Plasma membrane

Thin, ductile, elastic, phospholipid bilayer that enclosed the cytoplasm

Plasma membrane function

Osmosis barrier and controlling exchange of substances

What occurs within the plasma membrane

Electron transport and phosphorylation

Cell wall

Rigidity, and shape and barrier to lower molecular weight substances

Peptidocglycan

3 layered latticework layer

Gram +ve cell wall

Thick, compact and exclusively peptidoglycan

Gram -ve cell wall

Thin, less compact and more complex

What’s linked to peptidoglycan

Teichoic acids

In -ve gram cells wall OM and PG layer are separated by

Periplasmic layers

Porin

Channels to permit diffusion of smaller molecules

Non-porin

Anchoring OM to PG

Endotoxin

Toxic substance released by OM of bacteria

Lipopolysaccharide

Endotoxin with O antigen and inner and outer core

Lipid __ toxic for humans

A

Capsule

Anti-phagacitic properties and contribute to virulence factors

Virulence factors

Substances responsible for the ability for a bacterium to cause disease and illness

Adaptive immune evasion

Antigenic variation and phase variation

Antigenic disguise

Some bacteria coat themselves with host proteins

Immune suppression

Interference with B/T cells and neurophils

Intracellular survival

Hiding inside cells where they multiply

Release soluble antigen

Soluble antigens binds and neutralise antibodies before they reach the cell

Opportunistic infection

Infections from normal cells