Bacteriology Podcasts

Macroscopic Classification

• look at with naked eye

• colony morphology

• color

• smell

• narrows possibilities, but doesn’t provide diagnosis

Microscopic Classification

• using a microscope

• see shape: cocci, rods

• narrows possibilities, but doesn’t provide diagnosis

thick peptidoglycan layer

gram + bacteria

spores

mostly live in a vegetative state where bacteria can live and be extremely stable, but if their environment changes they can become active growing bacteria

capsule

sugar coating on bacteria that diminishes immune response

adhesions

forms really tight bond between bacteria and cells

biofilm

bacteria takes irregular form and gets deep into cells

aerobic

requires oxygen

anaerobic

no oxygen

facultative anaerobe

• can grow with or without oxygen

• corynebacterium

obligate anaerobe

• grows in the absence of oxygen

• clostridium

direct detection

first antibody has detector and binds to the epitope

indirect detection

second antibody has to recognize the first antibody to detect the epitope

immunofluorescent stain

if epitope is present, then antibody can bind, the sample glows and antibody can be found

enzyme-linked immunosorbent assay (ELISA)

• rapid strep, covid, pregnancy test

• uses antibodies to see whether or not a specific pathogen is present

• OR uses a specific pathogen to screen for antibodies against that pathogen

polymerase chain reaction (PCR)

• a definitive diagnostic that tells us if a nucleic acid is present

• the nucleic acid is present if the pathogen is present

• if primers are set up correctly, we can tell exactly what that pathogen is

regulation of gene expression

• bacteria can have lots of genes but not express them

• different genes are expressed in different environments

lag phase

• very few cells, no growth signals

stationary phase

• cells die and grow at same time

exponential phase

• happiest stage/most growth

decline phase

• run out of nutrients so cells die

transformation

• bacteria picks up DNA from environment and gains new genetic traits

transduction

• bacteriophages come out of cells, take DNA with them, and transfer that DNA to a new cell

conjugation

• bacteria mates and transfers plasmids from one cell to another

transposition

• moving DNA within the genome and affects gene expression

proteases

break down antibodies

variable surface proteins

changes antigens and stays one step ahead of immune system

endotoxins

• part of pathogens structure

• LPS in gram negative

exotoxins

produced and released by bacteria

A component of exotoxin

the actual toxin

B component of exotoxin

allows A to get into cell

superantigens

• harmful immune response

• triggers the release of cytokines by CD4+ cells

intoxication

• consume a lot of toxin and has immediate effect

infection

• accumulation of toxin

• requires time for reproduction of bacteria

• slower process - hours to days

bacteriostatic

• prevents growth

• fridge, freezer

bactericidal

• destroy bacteria

• bleach, cleaning wipes, soap

4 things bacteria must have to identify whether a particular pathogen is the cause of a disease (Koch’s Postulates)

• bacteria must be present in every case of disease

• bacteria must be isolated and grown in pure culture

• bacteria must reproduce when pure culture is put into healthy host

• bacteria must be recoverable from the experimentally infected host

antibiotics

• disruption of cell wall

• inhibit protein synthesis

• inhibit acid synthesis

• antimetabolite: human cells don’t use

antibiotic resistance

• changes target and uses alternative mechanisms

• pumps to remove antibiotic from cell

• degradation or modification of antibiotic