Microbiology Chapter 4: Dynamics of Prokaryotic Growth

Binary Fission

splitting in half

generation time

the time required for a cell to divide in half

Biofilms

communities surrounded and encased in mesh-like polymers cells, communicate within, form channels for the movement of nutrients and wastes throughout the community, are more protected from disinfectants and medicines and can be more of a disease threat (capsule, dome)

lag

metabolic activity but little splitting in half

log

active reproduction, divide quickly

stationary

nutrients get exhausted, waste products build up, so reproduction slows

decline

cell dies due to no nutrients and too much waste

psychophiles

microbes that grow in cold temps

mesophiles

microbes that grow between 25 and 45c (room and body temp)

thermophiles

microbes that grow in hot environments

acidophiles

microbes that grow in low pH

alkaliphiles

high pH

neutrophils

around pH of 7

halophiles

require salt to grow or grow in presence of alot of salt

refrigeration effect

slows microbe reproduction, often used to preserve food and microbial cultures

obligate aerobes

require oxygen to live

facultative anaerobes

can live with or without oxygen

obligate anaerobes

can’t use oxygen, harmed by it

microaerophilic

requires less oxygen than amount in air

aerotolerant microbes

cannot use oxygen, not harmed by it

toxic oxygen containing molecules

superoxide free radical (O₂^-)

hydrogen peroxide (H₂O₂)

Hydroxide (OH-)

plasmolysis

cell membrane shrinks, usually caused by water loss

photoautotroph

use light as energy source, CO2 as carbon source

ex. plants, algae, some bacteria

photoheterotroph

light as energy source, organic compounds as carbon source

ex. some green and purple bacteria

chemoautotroph

inorganic source of energy, CO2 as carbon source

ex. unusuak

chemoheterotroph

glucose for energy and carbon source

ex most bacteria, all fungi, protozoa, animals

culture medium

nutritious material that microbes grow in/on

culture

microbes growing in a container of medium

agar

jelly-like polysaccharide taken from algae, microbes grow on surface

complex media

variety of different ingredients

chemically defined media

exact chemical composition is known

selective media

cause certain microbes to grow while suppressing others

differential media

reacts with different microbes in different ways that are usually visible

enrichment culture

provides conditions that enhance the growth of a particular species

three ways of perserving culture

refrigeration, deep freezing, lyophilization(freeze drying)

hemocytometer

counting cells ons lide that contains a grid

culture counter

counting cells as they pass through a laser or electrical field

plate counts

determining the number of colonies growing on agar in a petri plate, only alive cells, most accurate

MPN(most probable numbers)

provides an estimate based on dilutions and cloudiness, amount of gas production or some other characteristic, often the largest dilution at which there are no more bacteria

turbidity

cloudiness, runs with cell number, not accurate