growth b

Microbial Growth

“Because individual cells grow larger only to divide into new individuals, microbial growth is defined not in terms of cell size but as the increase in the number of cells, which occurs by cell division."

Bin

ary

Fis

sion Note nascent septum forming

Pla

nes

of D

ivis

ion

(1/3

)

Diplococcus

Streptococcus

Pla

nes

of D

ivis

ion

(2/3

)

Tetrad

Sarcinae

Pla

nes

of D

ivis

ion

(3/3

)

Staphylococcus

Exp

onen

tial G

row

thNote Logarithmic Scale

Exp

onen

tial G

row

th

Sta

ndar

d B

acte

rial G

row

th C

urve

(1/

2)

Log Phase

Con

tinuo

us C

ultu

re

Sta

ndar

d B

acte

rial G

row

th C

urve

(2/

2)

Decline (Death) Phase

Solid Medium

Bacterial Colonies

• Standard Bacterial Count

• Colony-Forming Units

• Plaque-Forming Units

•Spread Plate

• Pour Plate

• Soft-Agar Overlay

Soft Agar Overlay

Spr

ead

& P

our

Pla

tes

Dilutions and Limitations

Serial Dilution

Direct Microscopic Count

Mos

t Pro

babl

e N

umbe

r M

etho

d

Mos

t Pro

babl

e N

umbe

r M

etho

dMost Probable Number Calculations

(based on 5 tubes/dilution)

dilutions (100 = 1 ml culure)

100 10-1 10-2 10-3 10-4 MPN/ml

5 5 1 0 0 33

4 5 1 0 0 33

5 4 4 1 0 40

5 4 4 0 1 40

5 5 5 5 2 5400

0 0 1 0 0 0.20

4 4 1 1 0 4.7

Det

erm

inat

ion

of T

urbi

dity

pH O

ptim

a

Neutrophiles

Aci

d-B

ased

Mic

robi

al S

ucce

ssio

n

Aci

doph

iles

Temperature Optima

Also Psychrotrophs & Thermodurics

Thermophiles

A large channel draining from a hot pool, containing carotenoid-rich microorganisms. The temperature of this channel in the foreground is about 60 oC. Layers of white-coloured limestone (forming a rock deposit known as travertine) can also be seen. Note the footprints of buffalo in the foreground. These animals often seek the warmth of thermal areas in the winter months.

limestone terraces formed by precipitation from calcium-rich water flowing from a raised hot pool. Pink, green and brown-coloured microorganisms occupy the thermal gradients in the flowing water (60-100oC)

Thermophiles

Deep-Sea Vents

Oxygen Requirements

Mic

roae

roph

iles

Cap

noph

iles

Gro

win

g O

blig

ate

Ana

erob

es

• Fluid Thioglycolate Medium

• Peptones, Yeast Extracts, Glucose

• Thioglycolate binds O2

• Agar slows diffusion of O2

• Resazurin is O2 indicator (red)

Salt Tolerance

Nutrient Acquisition—Exoenzymes

• Secreted into environment

• Catabolize food products

• Protease, DNAase, Amylase, Lipase

• Used in bacterial identification

Gro

win

g F

astid

ious

Mic

robe

s

Selective Media

Differential Media

Dia

gnos

tic M

edia

The concepts of Selective and Differential media can be confusing, particularly because very often media

are both Selective and Differential

Microbial Growth!

Win

ogra

dsky

Col

umn

AIRAIR

SANDSAND

SedimentSedimentCelluloseCellulose

CaSOCaSO44 + CaCO + CaCO33

WaterWater

Allows for the development Allows for the development of a redox gradient in a of a redox gradient in a sample, from anaerobic sample, from anaerobic through to Hthrough to H22S-richS-rich

Consists of water over Consists of water over sediment and substrate sediment and substrate (sometimes with sand)(sometimes with sand)

Other components (e.g.., Other components (e.g.., carbon sources, inorganic carbon sources, inorganic elements) often added.elements) often added.(these can be manipulated (these can be manipulated to select for different to select for different populations)populations)

Winogradsky Column

Example Winogradsky column Example Winogradsky column (from Atlas and Bartha 1999)(from Atlas and Bartha 1999)

Microbial ZonesMicrobial Zones reactionsreactions

Algae, cyanobacteriaAlgae, cyanobacteria COCO22 > CH > CH22O, HO, H22O > OO > O22

HH22S - oxidizersS - oxidizers HH22S > SS > S00, CO, CO22 > CH > CH22OO

Facultative anaerobesFacultative anaerobes CHCH22O > C0O > C02 2 + H+ H22

Purple non-sulfurPurple non-sulfur CHCH22O > HO > H22, CO, CO22 > CH > CH2200

photoheterotrophsphotoheterotrophs

Purple Sulfur BacteriaPurple Sulfur Bacteria HH22S > SS > S00, CO, CO22 > CH > CH22OO

Green Sulfur bacteriaGreen Sulfur bacteria H H22S > SS > S00, CO, CO22 > CH > CH22OO

Sulfate reducersSulfate reducers SOSO442-2- > H > H22S, CHS, CH22O > COO > CO22

Fermentative heterotrophs Fermentative heterotrophs CHCH22O > COO > CO22 + H + H22

HH22OO

AIRAIR

SANDSAND

SedimentSedimentCelluloseCellulose

CaSOCaSO44 + CaCO + CaCO33

Aerobic

Microaerophilic

Anaerobic

H2S

RedoxRedoxGradientGradient