This document discusses carbon and energy sources for bacterial growth. It explains that autotrophs use CO2 as a carbon source while heterotrophs use organic carbon sources. Phototrophs use light as an energy source and chemotrophs use redox reactions. The document also discusses bacterial spores, describing them as dormant, resistant structures that help bacteria survive harsh conditions until nutrients return. It covers the structure, types, formation, and germination of bacterial spores.

1. Bacteriology
Presented by
D. Mona Othman Albureikan
Lectures (9,10)

2. Carbon and Energy Sources for Bacterial Growth
1- Carbon Source:
A) Autotrophs are self-feeders and use CO2 as a carbon source.
B) Heterotrophs feed on others and use organic sources of carbon.
2- Energy source:
A) Phototrophs use light as an energy source.
B) Chemotrophs use redox reactions of organic or inorganic compounds as an energy
source.

3. • All living organisms require a source of energy.
• Organisms that use radiant energy (light) are called phototrophs.
• Organisms that use (oxidize) an organic form of carbon are
called heterotrophs or (chemo)heterotrophs.
• Organisms that oxidize inorganic compounds are called lithotrophs.
• The carbon requirements of organisms must be met by organic carbon (a chemical
compound with a carbon-hydrogen bond) or by CO2.
• Organisms that use organic carbon are heterotrophs and organisms that use CO2 as a
sole source of carbon for growth are called autotrophs.
Carbon and Energy Sources for Bacterial Growth

4. Carbon and Energy Sources for Bacterial Growth

5. Carbon and Energy Sources for Bacterial Growth

6. • Photoautotrophs obtain energy by photophosphorylation and fix carbon from CO2 via
the Calvin-Benson cycle to synthesize organic compounds.
• Cyanobacteria are oxygenic phototrophs (noncyclic). Green sulfur bacteria and purple
sulfur bacteria are anoxygenic phototrophs (cyclic).
• Photoheterotrophs use light as an energy source and an organic compound for their
carbon source or electron donor – can’t fix CO2.
• Chemoautotrophs use inorganic compounds as their energy source and carbon dioxide
as their carbon source.
• Chemoheterotrophs use complex organic molecules as their carbon and energy sources.
Carbon and Energy Sources for Bacterial Growth

7. Bacterial spore
• A bacterial spore is a structure produced by
bacteria that is resistant to many
environmental or induced factors that the
bacteria may be subjected to.
• Bacterial spores are highly resistant,
dormant structures (i.e. no metabolic
activity) formed in response to adverse
environmental conditions.
• Spore formation (sporulation) occurs when
nutrients, such as sources of carbon and
nitrogen are depleted.

8. Bacterial spore
• Spores help bacteria survive by being
resistant to extreme changes in the
bacteria's habitat including extreme
temperatures, lack of moisture
(Dehydration) , or being exposed to
chemicals and radiation, but it is still not
clear where they get nutrition from in
these conditions.
• Bacterial spores can also survive at low
nutrient levels, as well as being resistant to
antibiotics and disinfectants.

9. Bacterial spore
• These factors make it nearly
impossible to eliminate bacterial
spores, as they are found in many
places, especially in food products.
• The ability to form a spore just
before they die off, that will allow
them to resume life or become a
vegetative cell again if conditions
improve.
• It is a survival mechanism not a
reproductive method.

10. • Most bacterial spores are not toxic and cause little
harm, but some bacteria that produce spores can be
pathogenic.
• Most spore-forming bacteria are contained in the
bacillus and clostridium species but can be found in
other species of bacteria as well.
• There are different types of spores including
endospores, exospores, and spore-like structures called
microbial cysts.
• Each of these aid the bacteria in survival and serve as
protection for the cell.
Bacterial spore

11. Types of spores
• There are two types of spore
1) endospores.
2) exospores.
• Endospores- are formed within
the vegetative cell. (inside the
cell).
• Exospores- are formed in either
one of the ends of the vegetative
cell. (on the surface of the cell).

12. Structure of spore
• The outer and inner coat made up of
protein and they provides chemical
and enzymatic resistance to the
spores.
• Cortex region lies between the region
of outer and inner coat and it is made
up of peptidoglycon.
• Cortex helps in dehydration process
during sporulation process and thus
providing high temperature
resistance.

13. Structure of spore
• Germ cell wall protects from
potentially damaging chemicals and it
protects the central core.
• The central core portion consists of
DNA, small amounts of RNA,
ribosomes, enzymes and nearly 40%
of dipiclonic acid. (DPA)
• This DPA helps in preventing the
damage against DNA by chemicals
present in the environment.

14. The factors that plays major role for the
resistance of Bacterial Spore:
• Calcium dipicolinate in core
• Keratin spore coat
• New enzymes (i.e., dipicolinic
acid synthetase, heat-resistant
catalase)
• Increases or decreases in other
enzymes.

15. Sporulation
• The process of
production of spores is
called sporulation or
sporogenesis.
• The one vegetative cell
forms a single spore, which,
after germination, develops
into a new cell.
• It takes 8hrs-19 hrs to
compelete.

16. Endospores
formation

18. Exospores formation
• In exospores formation spores developed outside the body.
• They developed attached with a outer surface of the cell wall.
• During the unfavorable conditions Primarily, the mother cell and the daughter cells are
divided by means of the septum and later it forms a bud like structure at the outer
covering.

19. Exospores formation
• The cytoplasmic division results in the bud and it is covered by a double layered
membrane.
• Later it is followed by outer and inner coat development and thus resulting exospores.
• During favorable conditions the bud get detached from the body and it is followed by
germination.

20. Germination
• Sporulation is followed by germination.
• An endospores and exospores returns
to its vegetative state by a process called
germination.
• Germination is triggered by physical or
chemical damage to the endospores coat.

21. Germination
• When the environmental conditions
become favor of the bacteria, the spores
are reactivated and thus giving rise to a
new bacterial cell.
• This is not a process of reproduction.
• Vegetative cell produces a single spore
which in turn forms a new bacterial cell.