7. Metabolism of microbes (37)

1. Microbial Metabolism

2. Metabolism - all of the chemical reactions within a living organism

1. Catabolism
( Catabolic )
• breakdown of complex organic molecules into
simpler compounds
• releases ENERGY
2. Anabolism
( Anabolic )
• the building of complex organic molecules
from simpler ones
• requires ENERGY

3. Metabolism, the sum of catabolism and anabolism.

Catabolism
Larger
molecules
Smaller
molecules
Energy
Anabolism
Large, complex molecules are generally richer in energy than
are small, simple ones. Catabolic reactions break down large
molecules into smaller ones, releasing energy. Organisms
capture some of this energy for their life processes. Anabolic
reactions use energy to build larger molecules from smaller
components. The molecules synthesized in this way are used
for growth, reproduction, and repair.

4. For anabolism

All microorganism are divided on basis of
Carbon requirements:
➢ Autotrophs synthesize all necessary
components from CO2
➢ Heterotrophs use different organic
substances for synthesis their components

5. Different degree of bacteria heterotrophism

Saprophytes use dead organic substances,
and are independent from another organism
Parasites use organic material from an
alive organism

6. Ways of nutrients entering into bacterial cell

Passive diffusion (doesn’t need energy)
Facilitated diffusion (doesn’t need energy)
Active transport (occurs with the help of
carrier membrane proteins – permeases,
which are strictly specific for definite
substance)

7. The Model of Facilitated Diffusion

Outside cell
Inside cell
The membrane carrier (a)
can change conformation
after binding an external
molecule and subsequently
release the molecule on the
cell interior.
(b) It then returns to the
outward oriented position
and is ready to bind another
a
solute molecule. Because there is
no energy input, molecules will
continue to enter only as long as
their concentration is greater on the
outside.
Outside cell
Inside cell
b

8. Active transport is the transport of solute molecules to higher concentrations, or against a concentration gradient, with the

input of metabolic
energy.
Solute binding
protein
Periplasm
Transporter
Cytoplasmic
matrix
ATP
ADP
Nucleotide
binding
domain

9. Cultural Media

Must meet the following requirements:
➢ Contain water (all processes of vital activity
occur in water)
➢ Contain all necessary nutrients for definite
bacterium
➢ Possess suitable pH (often 7.2-7.4)
➢ Possess suitable osmotic pressure (more
commonly 0.87% NaCl)
➢ Must be sterile

10.

Osmotic Pressure

11. Classification of Cultural Media

In accordance with
the consistence:
➢ Liquid
➢ Semi-liquid
➢ Solid
Density of medium is reached by addition of
agar (polysaccharide from seaweed – red
algae): 1.5% for solid medium, 0.5% for
semi-liquid one

12. Liquid and Solid Cultural Media

Fannie Eilshemius (1850–1934)
and Walther Hesse (1846–1911).
Fannie Hesse suggested to her
husband Walther (a physician and
bacteriologist) that he should try
using agar in his culture medium
when more typical media failed to
meet his needs.

13. Classification of Cultural Media

In accordance with composition:
➢ Simple (Minimal) = Basic (Universal)
Eg.: peptone water, meat-peptone broth
(nutritious broth), meat-peptone agar
(nutritious agar)
➢ Complex = Simple + additional component
(single or some ones)
Eg.: blood agar, serum broth

14. Classification of Cultural Media

In accordance with application:
➢ Selective media – solid media favorable for
growing of one type of microbe but
suppress growing of other ones due to
presence of an inhibitor
Eg.: Yolk Salt Agar (YSA) – Staphylococci
Milk Salt Agar (MSA) – Staphylococci
Bismuth-sulfite agar – Salmonella
MacConkey agar - Salmonella, Shigella

15. Selective Cultural Media

16. Classification of Cultural Media

In accordance with application:
➢ Enrichment media – liquid media which
inhibit replication of contaminants and
permit multiplication of a pathogen. After
incubation for 1-2 days, this is plated on
selective or differential media
Eg.: Salt broth - Staphylococci

17. Classification of Cultural Media

In accordance with application:
➢ Differential media – for studying of
enzymic activity of bacteria, contain special
dyes and carbohydrates, allow distinguish
fermenting bacteria from non-fermenting
Eg.: Endo agar – Escherichia
EMB (eosin-methylene blue) agar – Escherichia
Giss media – definition of fermentatve spectrum of
bacteria

18. Differential media

19. Selective and Differential Media

MacConkey’s Agar (Плоскирев medium)
• used to isolate Salmonella and Shigella
MacConkey’s Agar
• Bile salts and crystal
violet (inhibits Gram (+)
bacteria)
• lactose
• pH Indicator
MacConkey
Many Gram (-) enteric non-pathogenic bacteria can
ferment lactose, Salmonella and Shigella can not

20. Selective and Differential Media

EMB
(Eosin Methylene Blue)
used to differentiate Eschericia from Salmonella
and Shigella
• dyes inhibit Gram (+) bacteria
• selects for Gram (-) bacteria
• lactose
• pH Indicator
•Many Gram (-) enteric non-pathogenic bacteria can ferment
lactose, pathogenic bacteria can not

21. Enzymes - catalysts that speed up and direct chemical reactions

A. Enzymes are substrate specific
• Lipases
Lipids
• Sucrases
Sucrose
• Ureases
Urea
• Proteases
Proteins
• DNases
DNA
Naming of Enzymes - most are named by adding
“ase” to the substrate

22.

Enzyme Specificity can be explained
by the Lock and Key Theory
E + S -----> ES ------> E + P

23. Groups of Enzymes

Grouped based on type of reaction they
catalyze
1. Oxidoreductases
oxidation & reduction
2. Hydrolases
hydrolysis
3. Ligases
synthesis using ATP
4. Transferase
5. Isomerase
transport chemical groups
isomer

24.

Enzyme Components include 2 Parts:
1. Apoenzyme - protein portion
2. Coenzyme (cofactor) - non-protein, many
are derived from vitamins
Holoenzyme - whole enzyme

25. Bacterial Enzymes Localization

Endoenzymes – act into bacterial cell
Exoenzymes – are excreted from the cell,
and act out of the cell. Pathogenic enzymes
are exoenzymes.

26. Fermentative spectrum of Bacteria

Is genetically coded quality dependent on
the species of bacteria
It is used for identification of bacteria
Ability to ferment any substrate can be tests
on Differential media (eg. Giss media)
A number of cultural media for studying of
bacteria biochemical activity with further
identification is called “color row”

27. Energy Production

Energy-producing metabolism (catabolism) is
the set of redox reactions, it occurs with
release of energy and synthesis of ATP
1. Oxidation
• refers to the loss of Hydrogen and/or electrons
2. Reduction
• the gain of Hydrogen and/or electrons

28. Types of Bacteria Respiration

Aerobes use O2 to break down complex
organic substances into simple ones
Anaerobes don’t use O2 to break down
complex organic substances into simple
ones
Facultative anaerobes can grow in both
presence or absence of O2

29. Aerobic Cellular Respiration

Electrons released by oxidation are passed
down an Electron Transport System (E.T.S)
with oxygen being the Final Electron
Acceptor.
General Equation:
Glucose + oxygen----> Carbon dioxide + water
C6H12O6 + 6 O2 -------> 6 CO2 + 6 H2O
38 ADP + 38 P
38 ATP

30. Anaerobic Respiration

Electrons released by oxidation are passed
down an E.T.S., but oxygen is not the final
electron acceptor
Final electron acceptor
Nitrate (NO3-)
----> Nitrite (NO2-)
Sulfate (SO24-)
----> Hydrogen Sulfide (H2S)
Carbonate (CO24-) -----> Methane (CH4)

31. Oxygen is lethal to some organisms

All organisms produce superoxide ( O2-)
Superoxide is toxic to cells (steals electrons)
Superoxide must be neutralized
Superoxide dismutase neutralizes O2-
O2- + O2- + 2 H+ -------> H2O2 + O2

32. Catalase

Hydrogen peroxide is also toxic to cells and
it must be neutralized
2 H2O2 --------> 2 H2O + O2
Obligate Anaerobes lack:
• Superoxide dismutase ( SOD )
• Catalase

33. Creation of Anaerobic Conditions for Bacteria Cultivation

Physical method – mechanical air elimination
from tightly closed space (anaerostat)
Chemical method – using chemical reagents
actively absorbed O2
Biological method - joint cultivation of
aerobes and anaerobes into hermetic closed
space (eg. Fortner plates)

34. An Anaerobic Work Chamber and Incubator

35. Special Cultivation Techniques

Microaerophilic Bacteria
grow best under reduced
O2 levels and increased
CO2 levels
Normal Atmosphere
21 % O2
3 to .03 % CO2
A. Candle Jar
16 % O2
4%
CO2

36.

Microaerophilic Bacteria
B. CO2 Generating Packet

37. Cultural Media for Anaerobes

Kitt-Tarocci medium – glucose broth with
the pieces of boiled liver
Glucose agar in high column
Wilson-Blair agar for Clostridia

38.

39. Coenzymes

1. Niacin
• NAD (Nicotinamide adenine dinucleotide)
2. Riboflavin
• FAD (Flavin adenine dinucleotide)
3. Pantothenic Acid
• CoEnzyme A