Microbial Growth, Resistance, and Sterilization: Key Concepts in Microbiology

Obligate aerobes

require oxygen for growth and have superoxide dismutase to break down toxic forms of O2

Obligate anaerobes

die in the presence of oxygen and use other compounds like nitrates and sulfates for growth

aerotolerant anaerobes

anaerobes use sulfates and nitrates as their electron acceptor, but can survive in the presence of air because they have superoxide dismutase to neutralize toxic forms of oxygen

facultative anaerobes

grow in air because they have superoxide dismutase and then use detoxified oxygen for aerobic respiration. When oxygen is absent, facultative anaerobes use nitrates and sulfates

Psychrophiles

bacteria that grow between -5 degrees celcius and 10 degrees celcius

Mesophiles

bacteria that grow between 20 degrees and 40 degrees celcius; the human pathogens are in this group

Thermophiles

Bacteria that grow between 40 degrees celcius and 65 degrees celcius

Hyperthermophiles

Bacteria that grow between 80 degrees celcius and some above 100 degrees celcius

Acidophiles

bacteria that grow in pH 1 - 4.5

Neutrophiles

bacteria that grow in pH 5.5 - 8.5

Alkalinophiles

bacteria that grow in pH 7.5 - 11.5

ID50

the dose that will cause an infection in 50 percent of the test population.

Quorum sensing

The ability of bacteria to sense the presence of other bacteria via secreted chemical signals and changing functions based off of populations

benefits of quorum sensing

less susceptible to environmental stress, like UV, temperature, pH, antibiotics

Water channels that diffuse nutrients into biofilm

Concentrated enzyme secretion

lag phase

Cells do not grow, cells adjusting to new environment, bacteria expressing gene expression.

log/exponential phase

Bacteria grow

stationary phase

Phase where bacteria no longer grow due to no food or change in environment(pH,temp)

Decline

cell death, gradually die over time

petrof-hausser chamber

used for counting bacteria, 1 ml of bacteria used

Sterilization

destruction of all microorganisms and viruses in and on an object

Aseptic

an environment or procedure free of pathogenic contaminants

disinfection

destruction of most microorganisms and viruses on non living tissue

Antisepsis

reduction in number of microorganisms and viruses on living tissue

Degerming

removal of microbes by mechanical needs

sanitization

removal of pathogens from objects to meet public health standards

Pasteruization

use of heat to destroy pathogens and reduce number of spoilage microorganisms in foods and bevages

statsis/static

suffixes indicating inhibition but not complete destruction of a type of microbe

cide/cidal

suffixes indicating destruction of a type of microbe

Antibiotics target

Cell walls, membranes, proteins, and DNA/RNA

Autoclave

Piece of equipment used to sterilize articles by way of steam under pressure (moisture)

Freezer

kills bacteria by freezing and thawing them

dry heat sterilization

Kills by oxidation

Flaming

Incineration

Hot-air sterilization

Filtration

traps particles with a netlike structure

Radiation

UV and Gamma

Characteristics of antibiotics

poison

selectively toxic

Ehrlich

Magic bullet(chemotherapy)

Fleming

discovered penicillin

Antibiotic -cell walls

permanent competitive enzyme inhibitors

inhibit peptidoglycan synthesis

R groups

help antibiotics target/make selective

Antibiotic - inhibit protein synthesis

stop specific functions of protein synthesis

ribosomes are different enough between pros & euks to have selective protein killing drugs

Tetracycline

kills 99% of protein in pros.

Kills 1% of protein in Euks.

Antiobiotics - target cell membrane

polymixins bind to to LPS

create a gap where cellular contents leak out

Antibiotics - inhibit general metabolic pathways

inhibit precursors of protein: inhibition of DNA & RNA synthesis

synergistic effect

when two different drugs increase the action of one or another drug

theraputic index

Used to compare the theraputically effect dose to the lethal dose

Spontaneous evolution

bacteria is created that is resistant to antibiotics

decreased influx

mutating to not take in as much of drug, which increases resistance

active efflux

cell mutates to have a pump that takes drug out of cell

Target site mutates

drug can no longer bind to enzyme

target protection proteins

blocks antibiotics from binding with proteins

Ames test

A procedure using bacteria to identify potential carcinogens

Recombination

the genetic process by which one chromosome breaks off and attaches to another chromosome creating a unique strand

Bacterial Genome + DNA fragment

after recombination create a new strand that is resistant

If dna fragment has no origin of replication

Dna cannot duplicate and apppears in only one daughter cell

if dna fragment has origin of replication by joining chromosome

Dna will persist in all progeny with new phenotype

Living Strain that is nonpathogenic + heat treated dead cells, what happens

Living strain takes Dna from dead cells and synthesizes capsules and becomes pathogenic(transformation)

Electroporation

cell receives high voltage and temporarily has holes in cell membrane allowing dna fragments to diffuse through

Lytic Cycle (transduction)

a viral reproductive cycle in which copies of a virus are made within a host cell, which then bursts open, releasing new viruses. But virus creates phage with DNA of bacteria and spreads new phenotype to all bacteria.

Congugation

bacterial exchange of genes between individual cells via the pilus. Donates plasmid dna to recipiant.