Microbial nutrition

Microbial nutrition
Growth of bacteria normally refers to a measure of population density from original inoculums. When culturing bacteria, it is very important to provide similar nutritional and environmental conditions that exist in its natural habitat. The culture medium must contain water, source of carbon, energy, growth factors, nitrogen and other chemical elements.
Culture of bacteria
Culture Media in Lab.
Culture media gives artificial environment providing with natural conditions necessary for growth of bacteria.
Culture media in Lab.
Microbial cells need basic requirements for growth as fallow:
A - Nutrient elements
Nutrients are substances used in biosynthesis and energy production such as:
1- Microbial cell composition is made up of several major elements like carbon , oxygen, hydrogen, nitrogen, sulfur, phosphorus, potassium , calcium, magnesium and iron are called macroelements because they are required in large amounts as components of carbohydrate , lipid , protein and nucleic acids synthesis.
2- Microorganisms require few microelements like manganese, zinc, cobalt, nickel and copper are available in nature have many roles in the cells, is a part of enzymes cofactors that make to catalysis of reaction and maintenance of protein structure.
A - Nutrient elements
3- Growth factors are organic compounds require as an essential cell components can’t be synthesis by M.O, there are three major classes of growth factors
a- purines and pyrimidines for nucleic acid synthesis.
b- amino acids are needed for protein synthesis .
c- vitamins are small organic molecules that are usually make all or part of enzymes and cofactors are needing in very small amounts to sustain growth such as folic acid , biotin , vitamins B12 and K.


C-Physical requirements for bacterial growth
There are some factors influence on microbial growth includes:
a- Temperature
b- Oxygen
c- pH




In this process, part of the genetic material of a donor cell is transferred to a recipient cell by one of the fallowing mechanisms:

a- Transformation
It is uptake of the naked free DNA of donor bacteria by a recipient bacteria, the taken fragment is incorporated in chromosomal DNA and expressed as a new character in the recipient cell

b- Transduction
It is transfer a part of DNA of the donor bacteria to recipient bacteria by bacteriophage (fig.)

c- Conjugation
Conjugation occurs through mating of two bacterial cells one of them carries plasmid (F +) and the other is plasmid (F-). Conjugation is a major phenomenon occur in nature and responsible for transfer of antibiotic resistant between bacteria

Virology: is a branch of biology concerned with study of viruses and some other virus-like agents. Viruses (Latin virus meaning "poison") are biological particles obligate intracellular parasitic M.O, which are smaller than bacteria and so could passes through bacterial filters, they have not contain nucleus, cytoplasm, cellular structures and no cell membrane but have genetic material and protein Viruses are known to be responsible for several disease of many living organisms.
General features

Viruses structure
Viruses characters

4- Characteristic shapes: viruses have several shapes like spherical (complex), helical, rod and polyhedral, sometimes with tails or envelopes.
Viruses characters
5- Viruses can be classified according to their:-
a- Morphology (size, shape, types of symmetry, presence of tail or envelope).
b- Biological properties such as pathogenicity , host range which refers to the type of host in which the viruses are able to replicate in them like animals , plant, insects and bacterial cell (bacteriophage) .
c- Type of nucleic acid, deoxyribonucleic acid( DNA), ribonucleic acid (RNA)
and single or double stranded, shape of nucleic acid linear or circular .
Lytic cycle of T4- phage in E. coli
There are five steps composed of lytic cycle as fallow:
1- Attachment
The first step in lytic cycle is attachment or adsorption of phage -T4 when the tail fibers recognize and attaches to specific region on the cell wall of E. coli called receptors site.

2- Entry
In the beginning, an enzyme in the tail breaks down the bacterial cell wall in the receptor site, then the sheath of tail contracts and drives the DNA core through the cell wall of E. coli and empty protein coat remains outside has no role in the cycle.
Viruses lytic cycle
3-Replication
After infection, viral DNA takes over the biosynthetic machinery of the host cell and uses it to produce the parts needed for production of new virus particles, viral DNA replaces the host cell DNA as a template for replication to produce more viral DNA and transcription to produce viral mRNA .Viral mRNA are then translated using host cell ribosome into viral proteins (protein coat) .

4- Assembly
The cell becomes a factory for making viruses, the phage DNA and protein are assembled to form 200-300 new phage.

5- Release
Lastly, the cell wall breaks down and new phages are released, those newly viruses can infect other cells and begins the cycle over again.

Method of viruses replication
viruses
Question of lecture

Do you think the conjugation process is a sexual reproduction or exchange of genetic material between two bacteria occur usually in nature?

It is merely genetic exchange process occur between two bacteria to transfer a segment of plasmid carry a genetic character such as resistance to antibiotics ,new metabolic pathway or tolerance to live in environment with toxicity minerals because the plasmid not required in growth and reproduction process in prokaryotic cells.



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