11th Class Biology Chapter 6 Kingdom Prokaryotae Monera Short Question Answers

Robert Koch formulated the germ theory of disease.

1. A specific organism can always be found in association with a given disease. 2. The organism can be isolated and grown in pure culture in the laboratory. 3. The pure culture will produce the disease when inoculated into susceptible animal. 4.It is possible to recover the organism in pure culture from experimentally infected animal.

The smallest bacteria (e.g., some numbers of the genus Mycoplasma) are about 100 to 200 nm in diameter, approximately the size of the largest viruses ( poxviruses)

These shapes are known as cocci, bacilli, spiral.

When the division of cell is in two planes it will produce a tetrad arrangement. A tetrated is a square of 4 cocci .

When the division is in three planes it will produce a sarcina arrangement . Sarcina is a cube of 8 cocci.

Spiral come in one of three forms, a Vibrio, a spirillum, or a spirochete. 

Exceptional shapes of bacteria are trichome forming, sheathed stalked, square, stare shaped, lobed shaped and filamentous.

(i) Atrichous bacteria are without any flagella. (ii) Monotrichous, when signal polar flagellum is present. (iii) Laphotrichous, when tuft of flagella is present only at one pole of bacteria (iv) Amphitrichous, when tuft a flagella at each of two pole is present. (V) Periticlious, When flagella surround the whole cell.

These are hollow, nonhelical, filamentous appendages. True pili are only present on grem negative bacteria. They are made up of special protein called pilin. Function: They are primarily involved in a mating process between cells called conjugation. Some pili function as a means of attachment of bacteria to virus surfaces.

Capsule is made up of repeating polysaccharide units, and of protein or of both. Capsule is tightly bound to the cell. It has a thicker, gummy nature that gives sticky characters to colonies of encapsulated bacteria.

Some bacteria are covered with loose, soluble shield of macromolecules which is called as slime capsule and slime provides greater pathogen city to bacteria and protects them against phagocytosis.

The cell of most bacteria (germ positive) have a unique macromolecule called peptidoglycan. Its amount virus in different types of bacteria. It is composed of framework of long glycan chains cross- linked with peptide fragments.

These are the circular, double, stranded DNA molicules. They are self- replicating and are not essential for bacterial growth an metabolism. They often contain drug resistant heavy metals, disease and insert resistant gens on them. They can move from one bacterium to another bacterium. Plasmids are important vectors in modern genetic engineering techniques.

Cysts are dormant, thick- walled, desiccation resistant forms and develop during differentiation of vegetative cells which can germinate under suitable condition. They are not heat resistant.

Some kinds of bacteria can synthesize organic compounds necessary for their structure and metabolism from simple inorganic substances. They are known as autotrophs. While those bacteria which cannot synthesize their organic compounds from simple inorganic substances are called heterophic.

Nutrition is a process by which nutrients are acquired from the surrounding environment and used in cellular activities such as growth and metabolism.

On the basis of energy source autotrophic bacteria can be divided into two categories (i) Photosynthetic autotrophs (ii) Chemosynthetic autotrophis

Soil is full of organic compounds in the form of hums. The hums is a material obtained by the partial decay of plants and animals.

Facultative bacteria grow either in the presence or absence of oxygen e.g,. E. Coli.

Many soil inhabiting bacteria have very extensive enzyme system that breaks down the complex substance of hums into simpler compounds. The bacteria can than absorb and utilize these simpler substances as a source of energy. E. g,. Rhodopseudomonas.

Lag phase is phase of no growth. Bacteria prepare themselves for division while Log phase is phase of repaid growth. Bacteria divide at exponential rate.

Biological control means of one type organisms by another type of organism. There is possibility that bacteria pathogenic to insects may eventually be used instead of insecticides. Thus bacteria would be a biological control of insects that destroy our crops and other ornamental plants.

1. High temperature, 2. Dry heat, 3.moist heat, 4, electromagnetic radiations, 5, members filters.

Super Blue green algae is basically expensive pound such. In which cyan bacteria is a singled called organism that produce its own food through photosynthesis. It served as a complete whole food “which contain 60% protein with all essential amino acids in perfect balance.

Akinetes are thick walled, enlarge vegetative cells which accumulate food and become resting cells.

Microbicidal effect is one that kills the microbes immediately. Microbistatic effect-inhibits the reproductive capactities of the cells and maintains the microbial population at constant size.

All cells in trichome are mostly similar in structure but at interval are found slightly large, round, light yellowish thick walled cells called as heterocysts.

Cyanobacteria have heterocysts, which are helpful in the fixation of atmospheric nitrogen.

Kingdom procaryotae Kingdom procaryotae consist of prokaryotic cells. In Greek the word Pro means “before” and caryon means”nucleus” Microbiologists place bacteria in two major categories: i) Eubacteria (from Greek words for “true bacteria”) ii) Archaeobacteria (from Greek words for “ancient bacteria”) a much smaller division.

Antone Van Leeuwenhoek” used a simple microscope to describe bacteria and protozoa with accurate drawings and descriptions and called these small creatures as “animalcules”. He firstly observed small creatures in rain water then confirmed these in saliva, vinegar, infusion and other substances.

His main achievement are the development of vaccines for disease anthrax, fowl cholera and rabies. He also made significant contributions in development of pasteurization process and development of fermentation industries. He proved that micro- organisms could cause disease.

They are found almost everywhere,in air, land, lakes, oceans., oil deposits, food, decaying organic matter, plants, man and animals. Some bacteria are always present and contribute towards the natural Flora. Others are present only in specific environments such as hot springs, slightly alkaline/ acidic soil, highly saline environment, in highly polluted soil and waters.

1. Diplococcus: division is in one plane but cocci in pairs. 2. Streptococcus: division is in one plane but cocci form long chain of cells. 2. Tetrad: the division of cell is in two planes. 3. Sarcina: The division is in three planes. 4. Staphylococcus: the division occurred in random planes and cocci are arranged in irregular, often grape – like clusters.

1. Bacillus is a single cell of bacteria. 2. Streptobacillus is a chain of bacilli. 3. Diplobacilli occur in pairs.

Vibrio is curved or comma shaped sriral. Spirillum is a thick, rigid spiral, Spirochete is a thin, flexible spiral.

Examples of cocci are Staphylococci aureas and Diplococci pneumonia. Examples of rod shaped bacteria are Escherichia coli and Bacillus subitillis. Examples of spiral shaped bacteria are Vibiro and Hyphomicrobium.

Koch and his colleagues invented many tenchniques concerning inoculation, isolation, media preparation, maintenance of pure cultures and preparation of specimens for microscopic examinations.

Specific structures like capsule, slime, flagella, pili, fimbriae and granule are found in certain bacteria.

When cocci occur in pairs then arrangement is diplococcus. Whereas when cocci form long chain of cells then arrangement is called as streptococci.

When division occurred in random planes it will produce a staphylococcus arrangement in which cocci are arranged in irregular, often grape- like clusters.

An average coccus is about 0.5- 1.0 micrometer (ɳm) in diameter.

A bacillus is a signal cell of bacteria while streptobacillus is a chain of bacilli.

When bacteria are without any flagella the condition is atrichous and when single polar flagellum is present then condition is called monotrichous.

If tuft of flagella is present only at one pole of bacteria, the condition is called lophotrichous and when tuft of flagella at each of two poles is present the condition is called amphitrichous.

When flagella surround the whole bacteria cell then condition is called peritichous.

Flagella are extremely thin, hair like appendages. They come out through cell wall and originate from basal body, structure just beneath the cell membrane in the cytoplasm. It is made up of protein flagellin.

Primary function of flagella is to help in motility. With the help of flagella, flagellate bacteria can detect and move in response to chemical signals which is a type of behavior called Chemotaxis.

Escherichia coli, a bacillus of about average size, is 1.1 to 1.5 µm wide by 2.0 to 6.0 µm long. Some spirochetes occasionally reach 500 µm in length. Whereas staphylococci and streptococci are 0.75 to 1.25 µ in diameter.

The cell wall of most bacteria (gram positive) have a unique macromolecule called peptidoglycan. It is composed of framework of long glycan chains cross-linked with peptide fragments. The intact cell wall also contains chemical constituents such as sugar molecules, teichoic acid, lipoproteins and lipopolysaccharide, which are linked to peptidoglycan.

Eubacteria: Eubacteria (Greek of “True bacteria”) and a much smaller division. Cell well is of peptidoglycan or murein. For e.gE.Coli.

Archacobacteria:The archacobacteria (Greek for “ancient bacteria”). Cell wall is of protein, Glycoprotein, polysaccharide, for e.g Methanogen bacteria.

A Dutch scientist “Antone Van Leeuwenhoek” (1673) was the first to report the microbes such as bacteria and protozoa.

He firstly observed small creatures in rainwater, then confirmed these in saliva, vinegar, infusions and other substances.

Robert Koch formulated the “Germ theory of disease”.

The postulates of germ theory of disease are:

1. A specific organism can always be found in association with a given disease.
2. The organism can be isolated and grown in pure culture in laboratory.
3. The pure culture will produce the disease when inoculated into susceptible animal.
4. It is possible to recover the organism in pure culture from experimentally infected animals.

Flagella: These are extremely thin, hair like appendages. They come out through cell wall and originate from basal body, structure just beneath the cell membrane in the cytoplasm. They are made up of protein Flagellin.

Functions: Primary function of flagella is to help in motility. With the help of flagella, flagellate bacteria can also detect and move in response to chemical signals which is a type of behavior called as chemo taxis.

On basis of presence of flagella, pattern of attachment of flagella and the number of flagella present bacteria are classified into different taxonomic groups:

Atrichous:Atrichous means bacteria are without any flagella.

Monotrichous:When single polar flagellum is present then condition is known as monotrichous.

Lophotrichous:If tuft of flagella is present only at one pole of bacteria then these are lophotrichous flagella.

Amphitrichous: Amphitrichous is a condition when tuft of flagella at each of two poles is present.

Peritrichous: In peritrichous form, flagella surround the whole cell.

Pilli: These are hollow, non-helical, filamentous appendages. Pilli are smaller than flagella and are not involved in motility. True Pilli are only present in gram-negative bacteria. They are made up of special protein called pilin.

Function:

1. They are primarily involved in a mating process between cells called conjugation process.
2. Some pili function as a means of attachment of bacteria to various surfaces.

Christian Gram developed the technique of gram stain.

Collectively complexes of layer external to the cell protoplasm are called a cell envelope.

Capsule: Bacteria produce capsule, which is made up of repeating polysaccharides units, and of protein, or both, capsule is tightly bound to the cell. It has a thicker, gummy nature that gives sticky characters to colonies of encapsulated bacteria.

Slime: Some bacteria are covered with loose, soluble shield of macromolecules which is called as slime capsule and slime provides greater pathogenicity to bacteria and protects them against phagocytosis.

It is a rigid structure. It determines the shape of bacterium. Cell wall also protects the cells from osmotic lysis.

The plasma membrane and everything present within it is known as protoplast.

The functions performed by cell membrane in bacteria are:

1. Cell membrane performed regulates the transport of proteins, nutrients, sugar and electrons or other metabolites.
2. The plasma membranes of bacteria also contain enzymes for respiratory metabolism.

Mesosomes: The cell membrane, invaginates into the cytoplasm forming structure called as mesosomes. Mesosomes are in the form of vesicles, tubules or lamellae.

Functions:Mesosomes are involved in DNA replication and cell division where as some mesosomes are also involved in export of exocellular enzyme. Respiratory enzyme are also present on the mesosomes.

Cell wall is only absent in mycoplasma.

Ribosomes are composed of RNA and proteins. Some may also be loosely attached to plasma membranes. They are protein factories. There are thousands of ribosomes in each healthy growing cell. They are smaller then eukaryotic ribosomes. They are 70S, small unit of 30S and large of 50S.

Many bacteria contains plasmid in addition to chromosomes. These are the circular, double stranded DNA molecules. They are self-replicating and are not essential for bacterial growth and metabolism. They often contain drug resistant, heavy metals, disease and insect resistant genes on them, Plasmids are important vectors, in modern engineering techniques.

Bacteria store glycogen, sulphurm fat and phosphate.

Common waste materials are alcohol lactic acid and acetic acid.