Bacterial Growth

binary fission

is an asexual process
cell elongation - due to intake of nutrients from environment and their conversion into new cellular material
replication of bacterial chromosome - occurs simultaneously with cell elongation
invagination of the cell wall
formation of transverse cell wall
separation into 2 new cells

bacterial growht

increase in total number of bacteria
refers to changes in a whole population of bacterial cells rather than changes to a simple organism

generation time

the time interval required for the bacterial cell population to double

lag phase

bacteria prepare to divide (gather nutrients, synthesize new protoplasm, elongate cells, replicate chromosome)

exponential phase

bacterial numbers increase lagarithmicallyst

stationary phase

nutrients become liniting and bacterial number remains constant

death phase

number of nonviable bacteria exceeds number of viable cells

dessication

drying of bacteria, leading to reduced metabolic activity and potential cell death.

phototroph

energy source is light

chemotroph

energy source is chemical

autotroph

carbon source is CO2
microbe builds up organic compounds

heterotroph

carbon source is organic
microbe breaks down organic compounds

psychrophiles

like it cool to cold
≤20°C

mesophiles

like moderate temps in the 20°C-45°C range with optimum at 37°C

thermophiles

like it hot
46-65°C

6.5-7.5

optimum pH range for bacterial growth

aerobes

grow in presence of free atmospheric O2

anaerobes

cannot grow in presence of free atmospheric O2

capnophiles

require 3-10% increase in CO2 concentration to initiate growth

halophiles

bacteria that require high salt concentrations for life

enriched

media containing additional growth factors beyond that of normal media to enhance growth of all bacteria, especially fastidious ones

Blood agar plates

enriched

chocolate

contains additional nutrients in readily accessible form
enriched

enrichment

used in clinical micro labs for intestinal specimens to increase likeihood of isolating intestinal pathogens
enhance growth of pathogens
inhibit growth of normal flora

selective media

promotes growth of one organism type and retards growth of others

Columbia Agar with Antibiotics

this media is selective for gram positive organisms

differential media

allows for the distinguishing of organisms growing on plated media to a substance included in the media
media formulation allows for the distinguishing of organisms due to a substance present in the media

MacConkey Agar

inhibits gram positive bacteria thereby selecting for growth of Gram negative bacteria
differentiates lactose fermenting GNR for lactose nonfermenting GNR
both selective and differential

mannitol salt agar

is a selective and differential medium that inhibits most bacteria except staphylococci and differentiates staphylococci based on their ability to ferment mannitol.