Basics of Microbiology for competitive exams

Basics of Microbiology

Basics of Microbiology

· Exo microbiology – Exploration of life in outer space.

· Antony – van – Leewan hooke – animal cules (or) little animals.

· Microbes arise from non living material – spontaneous generation (or) abiogenesis.

· “Grancis Appert” developed a technique of preserving food by cooling the tins and boiling. This process is known as “Appertisation”.

Basics of Microbiology

· Louis Pasteur – father of microbiology – developed narrow goose necked flasks Fermentation Pasteurization.

· John tyndall – Heat resistant phase and heat labile phase Tyndalization, Dust free chamber.

· The process of discontinuous boiling is called “Tyndalisation”.

Basics of Microbiology

· Heating ferment half an hour at 62.80C gives good products. This process is known as “Pasteurisation”.

· Von plenciz: proposed that the germs are responsible for disease (Germ theory of disease).

· “Etiology” is the study dealing with disease.

· O. Brefeld – Isolated a single cell of fungus for pure culture voing a solid medium “Gelatin”.

· Edward Jenner: use cowpox vaccine to immunize people against small pox.

· The culture which is kept long for many days it is said to be attenuated culture. These attenuated cultures as “Vaccines”.

Basics of Microbiology

· Alexander fleming – Pencillin (1929).

· Pure culture structure – Culture of a Micro Organism without any contamination.

· DNA can be altered by introducing a piece of new DNA by a process called “Recombination”.

· “E.V. Haeckel” proposed a separate kingdom called “Protista”.

· “Mesosomes” are present in prokaryotes absent in Eukaryotes.

· In prokaryotes cell wall chains Peptidoglycan layer.

1. Streptococci – Attached in Chains.

2. Staphylo cocci – Cells divide in any plane and are grouped in bunches.

3. Sarcinae – Divided in 3 plains and have cuboidal structure.

Basics of Microbiology

· Some bacteria contain multinucleate filaments – mycelium.

· Half curved (or) comma shaped – Vibroid.

· Bacteria which have more than one turn – Helical.

· “Flagellum” useful for the movement of bacterium.

· Protein of filament is “flagellin”.

· Bacteria move according to external stimuli are called “Tactic movement”.

· F pilus (Sex pilus) helps in the movement of genetic material from one bacterium to another bacterium.

· More number of cells are embedded in that coat, that coat is called “Slime”.

· Bacteria which require extreme conditions are grouped in “archebacteria”.

· Cell wall of eubacteria is made up of poly saccharides and lipids.

· After staining Gram +Ve appear deep violet; Gram –Ve – red colour.

· Site for synthesis of ATP – “Plasmalemma (or) Cytoplasmic membrane”.

· Cytoplasmic membrane appears to be infolded more than one point these infolding are called “mesosomes” – involve in binary fission.

Basics of Microbiology

· The spores are enclosed in Sac called “Sporangiospores”. If they are not enclosed they are called “Conidiospores”.

· “Strain” indicates the group of individuals derived from the initial pure culture.

· Clones: are derived from a single cell.

· Type strain: Is a strain, in which characters are fully studied and becomes a permanent example for that Sps.

· In DNA homology expts: if the “Heteroduplexes” are formed they will be considered that they are similar at the Sps. level. If no heteroduplexes are formed they are not similar at the Sps. Level.

· Sidero capsaceae: Bacteria of this family are generally found in iron containing water.

· Typoid – Salmonella typhosa / typhi

· Kingdom of prokaryote.
1. Gracilicutes – thin cell wall gram –Ve type.
2. Fermicutes – thick cell wall gram +Ve type.
3. Tenericutes – that have no cell wall – Mycoplasma.
4. Mendosicutes – Archeobacteria.

· Constituent of Co-enzyme A – Sulphur.

· If the source of carbon is CO2 the microbe is called an “autotroph”.

· If the source of carbon is organic compound it is called “heterotroph”.

· If the organism can grow on a single carbon source without the requirement of growth factory additional organic compounds the organism is called “Phototroph”.

· If as organism requires additional organic compounds or growth factors for their growth the growth is called “auxotroph”.

· “Chemoautotrophs” – utilizes CO2 in the presence of reduced inorganic compounds such as NH3, H2, H2S.

· Chemoheterotrophs – This group of bacteria uses organic compound as carbon and energy sources.

· Optimum pH of bacteria – 6.7 to 7.0.

· Facultative anerobic bacteria – They can grow either in the presence (or) absence of O2.

· Micro aerophilic bacteria – They require low levels of O2 concentration.

· Certain yeasts and moulds require higher concentration of sugars these are called “Osmophiles”.

· Certain bacteria require high concentration of salts for their growth and these are called “Halophites”.

· Most common method of multiplication in bacteria “Transverse binary fission”.

1. Lag phase – There will not be any cell multiplication.

2. Log phase – Cell multiply in an exponential manner. Primary metabolites produced.

3. Stationary phase – Because of limiting nutrient concentration and other factors the cells cannot continuously multiply. Secondary Metabolites

4. Death phase – During this phase some of the cells will be die and some cells will be active but will not multiply.

· For studying various physiological and metabolic activites, cells present in log phase are to be taken into consideration.

· Maintaining the culture continuously in log phase is known as “Coninurs culture”.

· Maintaining culture so that all the cells will divide at only one time called “Synchronus culture”.

· When all metabolites are synthesized at the relatively equal rates the growth is called “Balanced growth”.

· If a strain is supplied with two organic compounds it will exhibit a growth called “Diauxic growth”. Diauxic growth will have ‘two lag phases’ by J. Monaod.

· Micro scopic method of counting cells is usually done by using patroff – Hauser counting chamber.

· Indirect method – Plate count methods.

· The principle in plate count method is that each viable cell will give rise to a single colony.

· Membrane filter counting method: useful in a large volume of water (or) air.

· In turbidometric method the number of cells can be determined using a “Calorimeter”.

· In aerobic organisms O2 is terminal electron acceptor where as in anaerobic organisms Nitrate, Sulphate (or) CO2 will be electron acceptor.

Basics of Microbiology

· Under anaerobic condition pyruvate reduced to “lactic acid”.

· Pentose phosphate pathway also known as “Shunt glycolysis”.

· In this process only reduced NADP molecules can be produced and there is not production of ATP.

· Entner – Doudoroff (or) off pathway present in both aerobic and anaerobic prokaryotes. This is absent in Eukaryotes.

· Fermentation is anaerobic oxidation of organic compounds by micro organisms. It does not involve O2 (or) electron transport chain.

· “Glyoxylate pathway” is under taken by organisms where “acetate” is the major source of the organic carbon (or) where acetyl COA is produced without formation of “pyruvic acid”.

· In this cycle “Isocitrate lyase” and malate synthase” are specific enzymes for this cycle.

· Hill and Bendall proposed “Z-Schme” in which the components of photo synthetic units are arranged as per the redox potential.

· Viruses cause disease during replication in host cell.

· Viruses multiply inside host cells and released by the process of “lysis” – Lytic phage.

· The fully structurally matured virus capable of infecting the host is called virion.

· Bacteriophages become the tool for the viral and genetic research.

1. Lytic phase: When lytic phase infect, bacteria will immediately respond.

2. Temperate phase: Bacteria response is not immediately shown.

· The Nucleic acid of the bacteriophase is covered with a protein coat called “Capsid”.

· Capsid is made up of number of sub units called “Capsomeres”.

· Types of Bacteriophages:
A – type – Hexagonal head, rigid tail with tail fibres.
B – type – Hexagonal head and a flexible tail.
C – type – Hexagonal head and a short tail.
D – type – Hexagonal head without tail. The capsomers are large in size.
E – type – Hexagonal head without tail. The capsomers are small in size.
F – type – They are filamentous (rod shaped).

Basics of Microbiology

· The phages A, B and C are unique to bacteriophages.

D, E – are unique for animals and few plants.

F – is mostly present in plants.

A,B, C – contain double stranded DNA.

D,F – Contain single stranded DNA.

E – Contain single stranded RNA.

· Stanley – crystallized virus particles.

· Iwanowski – virus as filterable agent.

· Beijerinck – named virus as TMV.

· Virioids – They are smallest and infectious agents of plants and cause number of diseases to plants.

· Adoptation: The phenotypic changes that result due to variation in environment condition is called “adaptation”.

· Type of mutations:
1. Point mutation
2. Frame shift mutation

· Point mutation : This mutation results due to substitution of one neucleotide for another if the purine is substituted for another purine (or) called “Transition type of mutation”.

· If purine is substituted by pyramidine (or) vice versa it is called “Transversion” pyramidone for pyramodine it is type of mutation.

· Frame shift mutation – The change in the sequence of nucleotides may result in the production of mRNA which results in the synthesis of non-functional protein.

· The addition (or) deletion of nucleotide sequence is called Insertion (or) deletion mutations.

· Types of chemical mutagens:

1. Which react with DNA – Eg: Nitrous acid
2. Base analogs – 2 – amino purine.
3. Intercalating agents – Nitrogen mustand, Bromouracil, Acridine orange.
· Three types of gene transfer.

1. Conjugation – Transfer of genes between the cells when they are in physical contact with each other.

2. Transduction – Transfer of genes between the cells due to bacteriophages.

3. Transformation – Transfer of naked DNA to the receptor cell.

Basics of Microbiology

· Plasmid is circular and gets integrated with bacterial chromosome and it is known as “Episome”.

· Prophage: The bacteriophage which is capable of integrating with the bacterial chromosome.

· Lysogeneic bacteria: The bacteria carrying the prophase.

· “Induction” is a process where the substrate is required for the synthesis of enzymes.

· Structural genes are responsible for the determination of aminoacid sequence of the enzymes.

· The regulatory genes control the rate of synthesis of enzymes.

· “Operon” consists of both the structural genes and the regulatory genes.

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Basics of Microbiology

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