SHRIMATI INDIRA GANDHI COLLEGE THIRUCHIRAPALLI GENERAL MICROBIOLOGY

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1 SHRIMATI INDIRA GANDHI COLLEGE THIRUCHIRAPALLI Two marks: GENERAL MICROBIOLOGY 1.Define bacteria? These are microscopic,unicellular,prokaryotic organisms. Ehrenberg established the genus bacterium Their size ranges from 0.5m to 3micron they are in the form of rods, spheres, spirals.flagella, pili are present 2.Define halophiles? A microorganisms whose growth is accelerated by or dependent on high salt concentrations these are chemoorganotrophic, aerobic bacteria & approximately 17 to 23% Nacl for good growth. The cytoplasmic membrane and ribosomes are stable only at high concentrations of Kcl 3.What is capsule? The bacterial cells are surrounded by a viscous substances forming a covering layer or envelope around the cell wall. This layer is called capsule. It protect the cell against temporary drying by binding water molecules 4.Define gasvesicles? These are present in phototrophs &halobacteria.these enable the cells to alter their specific mass & to float in water.they lack the capacity for active movement. 5.What is chlorosomes?

2 These are pigment bearing membranous structure. They are in the form of thylakoids.they are involved in photosynthesis.they are found in photosynthetic bacteria 6.Define carboxysomes? These are present in autotrophic bacteria.these are polyhedrical bodies that are similar to the size of bacteriophages.it is found in nitrosomonas. 7.Define magnetosomes? These are cellular inclusions present in some bacteria they are sensitive to magnetic field. 8.Define phycobilisomes? Granules on the surface of thylakoids, which contain phycobilin pigment. 9.Define PHB? A chloroform soluble polymer of beta hydroxybutyric acid.it is occur in the form of intracellular granules within certain bacteria & can be stained by fat soluble dyes. 10.Give an account of cyanophycean & sulphur inclusions? Stores of bound nitrogen are found among the prokaryotes only in cyanobacteria. These contain cynophycin granules which consist of a specific polypeptide. 11.Define microbial taxonomy? It is the classification of microbes based on physiological, metabolic, genetic & size & shape. 12.Explain Haeckal s three kingdom concept? Kingdom;protista (bacteria,fungi,algae,protozoa) Kingdom;plantae Kingdom;animalia 13.Define fungi?

3 Nucleated spore bearing achlorophyllous organism which generally reproduces sexually & asexually & filamentous, branched, somatic structure surrounded by cell wall contain chitin or cellulose. 14.Define algae &? Algae are chlorophyll bearing thallophytes in the sex organs are either unicellular or multicellular & not protected by sterile envelope 15.What is protozoa? They are unicellular,nonphotosynthetic,eukaryotic organisms they are under the kingdom protista. Most are aquatic 16. Give any two culture collection centres? American Type Culture Collection centre Northern Regional Research Laborotory. Five Marks: 1.Explain the morphological types of bacteria? Morphology of bacteria The individual spherical bacterium is called micrococcus.some spherical bacteria are arranged in pairs and they are called diplococci(sl.diplococcus).when the cocci are arranged in four they a called tetracocci when the cocci are arranged in chains, they are call streptococci. When the cocci are arranged in clusters like a bunch of grapes they are called staphylococci 2 Explain the cellwall synthesis & cellwall gram positive?

4 Cell wall is a very rigid structure that gives shape to the cell. The main function is to prevent the cell from expanding and bursting of cell because of uptake of water the rigidity of the wall can be destroyed by very high pressure or other severe physical conditions. Most bacterial retain their original shape during after such treatments. Gram Positive Peptidoglycan is present It is made up of Polysaccharides and teichoicacids are present The outer membranes is absent It contain low level of lipids It cannot be affected by Lysozyme Eg; staphylococcus aureus 3.Explain the structure & function & types of flagella? Bacteria posses one or more long unbranched appendages called Flagella. They are used for locomotion Types: When the flagellum is present at one end is called monotrichous When the flagellum is present at both ends is called amphitrichous When the flagellum is present on the surfaces(body fully ) Are called peritrichous Function: It is used for locomotion It is used for attachment of host cells

5 4.Expain Whittaker s 5 kingdom concept? The first classification system to have gained is Robert H.Whittaker s 5 kingdom the classification are: Animalia: It includes animals & eukaryotic cells Plantae : It includes multicellular plants Monera: Bacteria Protista Fungi 5. what are the major characteristics used in taxonomy Characteristics used in taxonomy are; Morphological features are important in microbial taxonomy for many reasons Morphology is easy to study and analyze,particularly in eukaryotic microorganisms The morphological similarity often is a good indication of phylogenetic relatedness Many different morphological features are employed in the classification & identification of microorganisms Many growth characteristics are considered as physiological Characteristics. 6. Explain the structure of fungi? The plant body of a fungus consists of thread is called hypha A hypha consists of thin wall & has a inner lining of cytoplasm A hypha do not have cross walls

6 The cross walls are called septa a hypha with hypha with septa called septate The chemical composition varies.cellulose & chitin are rich in cellwall the aseptate hyphae have number of nuclei and is called coenocytic A fungal plant body usually consists of a mass of hyphae called mycelium. 7Explain the characteristics of algae? It is live in aquatic or moist habitats Chlorophyll & other photosynthetic pigments are found The are autotrophic in nutrition Starch is the common reserve food in algae They may be prokaryotic or eukaryotic Asexual & sexual reproduction takes place The plant body consists of either unicellular or multicellular 8.Explain rhodophyta? It includes 7 orders.it is also called red algae Red colour chromatrophores which contain excess of phycoerythrin,chlorophylls,carotenoids,xanthophylls,pyrenoits Asexual & sexual reproduction are common It may be unicellular or multicellular Cellwall is made up of polysaccharides & polyuronic acids Food reserves are stored as floridean starch It is mostly occur in marine water

7 Ten marks: 1.Explain the preservation method of microbes? There are six types of preservation methods.they are Transfer on fresh media; Microbial cultures ae maintained by periodic transfer on fresh sterile media in tubes the frequency of transfer varies with the organisms after growth the cultures are stored at 37ºc for days to keep the cultures viable to use appropriate growth medium temperature Overlaying with mineral oil The oil must be above the tip of the surface the method is simple &viability is high it stored at 0º-5ºc Lyophilization; The cell suspensions are placed in small vials which are then frozen by immersing in a mixture of ice & vaccum & stored at low temperature it provide long term survival without a change in characters Storage at low temperature; Cultures are frozen in the presence of glycerol or dimethylsulfoxide in liquid nitrogen at 196ºc this method is called gyogenic preservation Storage in sterile soil; It is used for preserving spore forming bacteria & fungi spore suspensions are added to sterile soil & dried at room temperature & stored at refrigerator Storage in silica gel; Bacteria & yeast are stored at silica gel for 1-2years

8 2.Explain the Asexual reproduction of algae? protoplasm of the cell divides into many small parts.each parts develop new plants.there are different spores are formed they are; Monospores; They are produced in monosporangium without cell division the mother cell develops in to monospore & it develop in to a new individual Statospores; These are thickwalled resting spores & it develop into a new individuals Paraspores; The spores are produced from triploid sporophyte Microspores; These are small spores the protoplast divides & develop in to a new individual Auxospores; It is produced in unfavourable conditions the protoplast divides &germinates &into a new individual Endospores; The spores are produced within the protoplasm & nucleus these are found in bluegreen algae. 3.Write the sexual reproduction of fungi? The process of sexual reproduction begins joining of two cells & their fusion of protoplasts called plasmogamy the sex organelles are called gametangia & they produce gametes there are different types of spores formed in sexual reproduction Ascospores; These are single celled spores are produced in a sac called ascus

9 Basidiospores; These are single celled spores formed from a club shaped structure called basidium. Zygospores; These are large, thick walled spores formed when the two hyphae are fuse together Oospores; These are formed from a female structure called oogonium fertilization of the eggs by male gamets & give rise to oospores The asexual reproduction are also takes place they are; Sporangiospores; These are single celled formed from sporangia alpanospores are non motile. Conidiospores; These are formed at the tip or side of hypha small spores are called microconidia large spores are called macroconidia. Anthrospores; These are formed from at the disjointing of hyphal cells. Chlamydospoes; These are resistant to adverse conditions these are formed from vegetative hypha. Blastospores; These are formed by budding. 4.Explain the isolation of bacteria & fungi? Isolation of bacteria; Soil sample is collected Serial dilution is performed It is plated on either nutrient agar The spread plate or streak plate or pour plate technique is performed.

10 Then it is incubated on 37ºc for 24 hrs. The colonies are formed. To detect the bacteria is done by biochemical test. Isolation of fungi; Soil sample is collected Serial dilution is performed It is plated on rose Bengal agar or potato dextrose agar. Then it is incubated on 37ºc for 4 days The colonies are formed. 5. What is carboxysomes&phb & capsules? These are present in autotrophic bacteria.these are polyhedrical bodies that are similar to the size of bacteriophages.it is found in nitrosomonas. A chloroform soluble polymer of beta hydroxybutyric acid.it is occur in the form of intracellular granules within certain bacteria & can be stained by fat soluble dyes. The bacterial cells are surrounded by a viscous substances forming a covering layer or envelope around the cell wall. This layer is called capsule. It protect the cell against temporary drying by binding water molecules.