Microbiology Vi sinh trong sữa

Microbiology

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Microbiology

Microbiology is the study
of organisms which are
so small that they can
only be seen with the aid
of a microscope. Size is
measured in micrometer.
5 µm

1 µm = 0,001 mm
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Micro-organisms
Groups
Protozoa
Algae
Fungi
- Yeast
- Mould
Bacteria
Viruses

Range of Size
2 - 200 mm

1 mm - a few meters
5 - 10 mm
2 - 10 mm by meters
0,5 - 5 mm
0,015 - 0,2 mm

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Micro-organisms in the Laboratory

cfu,
colony
forming
unit

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Microbial Loads

Locality

CFU/hour
2
and100cm

Mibi
Picture

16
240
40

Gram pos.
bacteria
dominate

280
320

A lot of
gram neg.
bacteria

150

Moulds
dominate

In-doors: Dry environment
Office far from people
Office close to people
Corridor people passing
In-doors: Wet environment
Toilets
Cleaning room
Out-doors environment
Lawn far from people

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Shapes of Bacteria
Spherical

Rods

Curved or
Spiral

c
)

b)
a
)
d
)

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The Bacterial Cell - Basic Structures
Cell wall(1)
Cell membrane(2)
Chromosome(3)
1

2

3

4

Cytoplasm(4)

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Bacterial Cell - Structures

Cell wall

Pili

Cell
membrane

Cytoplasma with
ribosomes

Capsule
Granule

Mesosome

Chromosome

Flagellum

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Bacteria :
Function of Cell Structures
CELL WALL

◊ giving the cell its specific shape
◊ protects the cell against high
pressure and mechanical forces

CELL MEMBRANE

◊ acts as osmotic barrier
◊ active transport of nutrients and
metabolites

CYTOPLASM

◊ place of production

CHROMOSOME

◊ carrier of genetic information

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Bacteria :

Grampositive and Gramnegative

mainly
peptidoglycan
s

lipopolysaccharides

cytoplasm

peptidoglycans

cytoplasm

cellmembrane
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Gram+ and Gram- Bacteria
Gram-positives

Gram-negatives

∗ Micrococcus

∗ Pseudomonas

∗ Streptococcus

∗ Coliforms

∗ Staphylococcus

∗ Salmonella

∗ Lactobacillus

∗ Shigella

∗ Corynebacterium ∗ Serratia
∗ Actinomyces

∗ Yersinia

∗ Bacillus

∗ Vibrio

∗ Clostridium

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Bacterial Spores
Vegetative cells
Multiplication
Sporulating
cell

The Dormant Spore

Outgrowth

Germination
Mature spore
Core
Cortex

Exosporium
Membrane

Coats

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BERGEY´S MANUAL OF

Systematic Bacteriology
Classification and Identification of
Bacteria

including
ecology, enrichment, isolation and preservation

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BERGEY’S MANUAL OF
DETERMINATIVE BACTERIOLOGY

8th edition 1974
• 19 Parts
• 48 Families
• 245 Genera
• 2000 Species
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BERGEY’S MANUAL OF
DETERMINATIVE BACTERIOLOGY

Ninth Edition
1994
Identification of
Bacteria
35 Groups
550 Genera
4 500 Species
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Multiplication of bacteria
1 ⇒ 2 ⇒4 ⇒8⇒16⇒32…
20 ⇒21⇒22⇒23⇒24⇒25…

Nt = N0 x 2n

t
n= g

t
lg Nt = lg N0 + g x lg 2
g = generation time, i.e. the time for duplication
n = number of generations
t = incubation time, i.e. the time for growth
N0 = number of bacteria at time zero
Nt = number of bacteria at time t
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Generation Time

temp.(oC)

Bacterium

medium

g(min)

E. coli
E. coli

milk
37
glucose+minerals 37

12
90

Streptococcus lactis

milk

37

26

Lactobacillus acidophilus milk

37

75

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as
Ph
e

Log
Pha
se

Stationary Phase

ath
De

Log No of Bacteria

The Bacterial Growth Curve

Time
Lag Phase
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Fungi
Yeast

Mould
spores

sporophore

mycelium
budding
hypha

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Fungal Spores
Sexual

Asexual
chlamydospores
conidiospores

zygospore

ascospores
sporangiospores

basidiospores
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Reproduction of Moulds

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Reproduction of Yeast

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Important Growth Factors

Oxygen
Water

Nutrients
pH

Temperature

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Growth factor - Oxygen
Bacteria
all types of relationships
Moulds
are strictly aerobic organisms
with a few exceptions…..

Yeasts
are facultative anaerobic organisms
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Growth factor - Oxygen
Aerobic
Demand of
oxygen
Can use oxygen
at atmospheric
pressure

Facultative
anaerobic
Can switch
between oxygen
utilisation and
“fermentative”
metabolism

Anaerobic
No need of oxygen
Oxygen most
often toxic

Microaerophilic
Demand of oxygen
Can only use
oxygen at lower
pressure than
atmospheric
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