Free Kingdom Prokaryotae MCQs with Answers

521. Murein cell-wall is composed of:

• A. Sugar and amino acids
• B. Calcium pectate
• C. Glycoprotein
• D. Peptidoglycan

Explanation: Bacterial cell walls are made of peptidoglycan, also called as murein, which is made from polysaccharide chains cross-linked by unusual peptides containing D-amino acids.

522. Rhizobium belong to sub group of bacteria called:

• A. Alpha-Protobacteria
• B. Beta-Protobacteria
• C. Gamma-Protobacteria
• D. Delta-Protobacterla

Explanation: Proteobacteria is a phylum of gram-negative bacteria. The Proteobacteria are further divided into 5 classes: Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Deltaproteobacteria, and Epsilonproteobacteria.The first class of Proteobacteria is the Alphaproteobacteria, many of which are obligate or facultative intracellular bacteria. Some species are characterized as oligotrophs, organisms capable of living in low-nutrient environments such as deep oceanic sediments. Rhizobium is a genus of alphaproteobacteria. Rhizobium are gram-negative nitrogen-fixing bacteria that occur either as free-living soil bacteria or in interaction with the roots of leguminous plants.

523. The interval between two successive division of bacteria is called:

• A. Ecological time
• B. Population time
• C. Growth time
• D. Generation time

Explanation: Generation time is the time it takes for a population of bacteria to double in number or the interval between two successive divisions in bacteria. For many common bacteria, the generation time is quite short, 20-60 minutes under optimum conditions.

524. Most disease symptoms appear during.

• A. Lag phase
• B. Log phase
• C. Die
• D. Generation time

Explanation: After the lag phase, bacterial cells enter the exponential or log phase. This is the time when the cells are dividing by binary fission and doubling in numbers after each generation time. Metabolic activity is high as DNA, RNA, cell wall components, and other substances necessary for growth are generated for division. In humans, the disease symptoms develop during the log phase because the bacterial production attains such a high level which damages the tissues.

525. Endotoxins are released only when bacteria

• A. Excrete
• B. Reproduce
• C. Decline phase
• D. Stop phase

Explanation: At the decline phase, bacterial growth decreases exponentially and many bacteria begin dying due to lack of nutrients or unfavorable changes in body conditions. Endotoxins are components of bacterial gram-negative membranes that are released to the external environment when a bacterial cell dies. Bacteria don't excrete endotoxins as waste material.

526. Archaea live in both extreme and moderate environments those living in extreme condition are called:

• A. Extremophile
• B. Methanogen
• C. Extremophyte
• D. Extremogeus

Explanation: The correct term for organisms that live in extreme environments is extremophile. These organisms have adapted to survive in harsh conditions such as extreme heat, cold, acidity, or salinity, which would be detrimental to most other life forms.The other options are incorrect for the following reasons:Methanogen: While methanogens are a type of extremophile, the term specifically refers to those archaea that produce methane, and not all extremophiles are methanogens.Extremophyte: This term inaccurately combines concepts and is not used in scientific contexts to describe extremophiles.Extremogeus: This is not a recognized term and appears to be a misspelling or misunderstanding of 'extremophile'.

527. The Sulphur Bacteria which obtain energy by oxidizing H2S instead of water is called:

• A. Alpha proteobacteria
• B. Beta proteobacteria
• C. Gamma proteobacteria
• D. Delta proteobacteria

Explanation: The correct answer is Gamma proteobacteria. This group includes chemolithotrophic sulfur bacteria, which are capable of oxidizing H2S to obtain energy. This oxidation process releases energy that the bacteria utilize for growth and reproduction. These bacteria play a crucial role in the environment by participating in the sulfur cycle and have potential applications in biotechnology.In contrast, Alpha proteobacteria and Beta proteobacteria typically use organic compounds for energy, and Delta proteobacteria are more commonly associated with sulfur compound reduction rather than oxidation.

528. The first that oxygenated the atmosphere were:

• A. Cyanobacteria
• B. Phototrophic organisms
• C. Anaerobic organisms
• D. All of the above

Explanation: It is a fact that the first organisms that oxygenated the atmosphere were cyanobacteria

529. Rhizobium belongs to:

• A. Beta-protobacteria
• B. Gama-protobacteria
• C. Alpha-protobacteria
• D. Delta-protobacteria

Explanation: Rhizobium belongs to alpha proto-bacteria, this is a fact and has to be learnt

530. Myxospores are the spores produced by:

• A. Fungi
• B. Bacteria
• C. Algae
• D. Plants

Explanation: Myxospores are actually not spores produced by fungi, but rather by certain groups of bacteria called Myxobacteria. These bacteria are known for their unique life cycle, which involves the formation of myxospores under certain conditions. These myxospores are specialized structures that allow the bacteria to survive unfavorable conditions and then germinate when conditions become more favorable. So, in short, myxospores are produced by Myxobacteria, not fungi.