Following are bacteria test questions important for test and papers.
- Give composition or cell wall of bacteria?
Ans: The cell walls of most bacteria have a unique macromolecule called peptidoglycan. Its amount is different in different types of bacteria. It is composed of long framework of glycan (glucose) chains. These glycan chains are linked with peptide fragments. The intact cell wall also contains some molecule of sugar, techoic acid, lipoproteins and Lipopolysaccrides. These molecules are linked to peptidoglycan.
- What are Gram Positive bacteria? Give composition of their cell wall?
Ans: They are stained purple with this staining technique. They form CV- l complex (Crystal violet complex l) and retain the primary dye color. Gram positive bacteria have simple cell wall. It has large amount of peptidoglycan. It has (lesser) small amount of lipopolysaccharides.
- What are Gram Negative bacteria? Give composition of their cell wall?
Ans: They are stained pink with this staining technique. They retain secondary dye color. Gram negative bacteria have lesser amount of peptidoglycan. It has more complex structure. An outer membrane of lipopolysaccharides is present outer to the peptidoglycan layer. Gram negative species are more dangerous than the Gram-positive bacteria. The lipopolysaccharides layer is often toxic. This layer protects the bacteria from the immune system of host. Gram negative bacteria are more resistant to antibiotics.
- What are capsules? Give their function?
Ans: Some bacteria produce capsule outside the cell wall. It is made up of repeating units of polysaccharides or proteins or both. The capsule is tightly bound with the cell wall. It has thick and gummy nature. It makes the encapsulated bacteria sticky.
- What are pili? Give their functions?
Ans: Pili are hollow, non-helical and filamentous appendages present on cell wall. Pili are smaller than the flagella. True pili are present only in gram-positive bacteria. They are made up of special proteins called pilin. Pili are not involved in locomotion. They are primarily involved conjugation. Conjugation is a mating process. Some pili are used for the attachment of bacteria with various surfaces;
- What are the functions of flagella?
Ans: The primary function of flagella is locomotion. Bacteria can detect a chemical signal with the help of flagella and move in its response. Such type of behavior is called Chemotaxis.
- What are mesosomes? Give their functions?
Ans: The cell membrane invaginates to form mesosomes. Mesosomes are in the form of vesicles, tubules or lamellae. Mesosomes are involved in DNA replication and cell division. Some mesosomes are also involved in the export of exocellular enzymes. Respiratory enzymes are also present on the mesosomes.
- What are plasmids? Give their functions?
Ans: Plasmids are circular, double stranded extra chromosomal DNA molecules in bacteria. Many bacteria contain plasmids in addition to chromosomes. They are self – replicating bodies. Plasmids are not essential for the bacterial growth and metabolism. Plasmids contain drug and heavy metals resistant genes. Disease and insect resistant genes are also present on them. Plasmids play an important role in conjugation.
- Differentiate between cyst and spore?
Ans: The metabolically dormant (inactive) bodies with thick wall are called spores.
While the dormant, thick- walled and desiccating resistant structure is called Cyst.
- What is endospore? Give its function?
Ans: Bacteria also develop single endospore. Endospores are used to pass unfavorable conditions. The endospore germinates in favorable condition and develops new single bacterium. So, endospore formation is not a mean of reproduction.
- What are Phototropic anaerobic bacteria?
Ans: They are photoautotrophs. They have different photosynthetic equipment than plants. They use H2S as electron source. They are anaerobes. They found in ponds lake, and ocean sediments. They have different groups like bacteria and the green bacteria.
- What is chromoplasm?
Ans: The outer region is blue green pigmented. It is called chromoplam. Chromoplasm contain pigments chlorophyll carotene, myxothanhophyll and phycocyanin. It also contains oil droplets and glycogen. Certain gas vesicles are also present in it.
- What are Hormogonia?
Ans: The broken pieces of a filament arc called hormogonia. Double concave discs of gelatinous material are formed between two cells. It is called separation disc. The filaments break at these point and form hormogonia.
- What are Hormospores?
Ans: Under unfavorable conditions, some hormogonia develop thick wall. They are called hormospores. They germinate directly into new filament in favorable conditions.
- What are Akinetes or arthrospores?
Ans: Akinetes are thick walled, enlarge reproductive cells. The cell stores reserve food and enlarges. It secretes thick wall and become akinete. Akinete has outer wall exospore and inner wall endospore. They are yellow or brown colored. The akinete germinate immediately after raining.
- What are nitrifying bacteria? Give example?
Ans: Several bacteria in soil oxidize ammonia or ammonium ions in to nitrates. These bacteria are called nitrifying bacteria. This oxidation is known as nitrification. Nitrates are absorbed by plants, Example of nitrifying bacteria is Azobactor.