Biological Classification Test - 91

• Spirochete, (order Spirochaetales), also spelled spirochaete, are a group of spiral-shaped bacteria, some of which are serious pathogens for humans, causing diseases such as syphilis, yaws, Lyme disease, and relapsing fever. Examples of genera of spirochetes include Spirochaeta, Treponema, Borrelia, and Leptospira.
• Spirochaete bacteria are exceptional in showing fast locomotion through thick mucus because of the presence of additional bundles of elastic fibres.
  
• So, the correct answer is 'Additional bundles of elastic fibres'.

Nitrogen fixation is a process in which atmospheric nitrogen is converted into nitrites and nitrates to be absorbed by plants. Plants can not take nitrogen present in the atmosphere directly, certain bacteria help to fix atmospheric nitrogen to ammonium or nitrate. There are two types of nitrogen-fixing bacteria: symbiotic (Rhizobium and Frankia) and free-living (Azotobacter and Clostridium).
Frankia is filamentous, it is found in the root nodules of trees like Ulnus and Casurina.
Azospirillum is an aerobic, free living, nitrogen fixing bacteria. It is found in association with plant roots where it plays important role in plant growth and fixes atmospheric nitrogen.
Clostridium is a non-photosynthetic nitrogen-fixing genus.
Nitrogen fixation in Azotobacter takes place in the roots of tropical grasses.

In 1886, Adolf Mayer first described the tobacco mosaic disease that could be transferred between plants, similar to bacterial infections.
Wendell Meredith Stanley in 1935 who showed that TMV remains active even after crystallization. Tobacco mosaic virus was the first virus to be crystallized. It was achieved by 
Howard Martin Temin (December 10, 1934 - February 9, 1994) was a U.S. geneticist. Along with Renato Dulbecco and David Baltimore, he discovered reverse transcriptase in the 1970s.
Felix d'Herelle was a French-Canadian microbiologist, the co-discoverer of bacteriophages and experimented with the possibility of phage therapy. D'Herelle has also been credited for his contributions to the larger concept of applied microbiology. Thus, the correct answer is option B.

The above-ground parts of plants are normally colonized by a variety of bacteria, yeasts, and fungi. While a few microbial species can be isolated from within plant tissues, many more are recovered from the surfaces of healthy plants. The aerial habitat colonized by these microbes is termed the phyllosphere, and the inhabitants are called epiphytes. The phyllosphere, which is dominated by leaves, represents one of the largest terrestrial habitats for microorganisms, which influence their hosts with respect to growth and resistance to abiotic and biotic stresses. 

Xerosere or xerarch succession begins on exposed parent rocks (lithosere) or dry sand (psammosere). The stages are crustose lichen stage (pioneers), foliose lichen stage, moss stage, herbs stage, shrub stage, forest stage (climax stage). In this pioneer, plants are lichens, mosses and Selaginella, that help in soil formation.

Shigella sonnei is a non-motile, non-spore forming, facultative anaerobic gram-negative bacterium. Its non-motile characteristic means that this species does not have flagella to facilitate its movement like many other human enterobacteria. Shigella sonnei is a rod-shape bacterium and is lactose-fermenting bacterium causing dysentery.

Solution:

Correct answer is option B

Explanation for correct option:

• An endospore is a dormant, tough, non-reproductive structure produced by a small number of bacteria from the Firmicute family. 
• The primary function of most endospores is to ensure the survival of a bacterium through periods of environmental stress. 
They are therefore resistant to ultraviolet and gamma radiation, desiccation, lysozyme, temperature, starvation and chemical disinfectants. 

• Endospores are commonly found in soil and water, where they may survive for long periods of time. 

Amoeba is a organism, which has the ability to alter its shape by extending and retracting pseudopodia. Most amoeba do have contractile vacuole, which expels excess water from the cell.
Paramoecium is a unicellular ciliated Protozoa i.e, it possesses cilia. Paramecium demonstrate rotational cytoplasmic streaming, in which most cytoplasmic particles and organelles flow along permanent route, in a constant direction, which is known as cyclosis.

Osmosis is the movement of across a semi-permeable membrane driven by the osmotic pressure gradient. Water moves from the region of high osmotic pressure to that of the lower one. Plasma membrane is highly permeable to water since water can move through protein channels. The presence of salt increase the osmolarity of pickle and the water moves out of bacterial cell causing them to shrink, i.e., plasmolysis. Thus, the correct answer is option A. 

In helotism, the mycobiont is superior over phycobiont and such a relationship is called master and slave association e.g., in lichen. The fungal partner is called as mycobiont and the algal partner as phycobiont. In this relationship, fungi act as master and algae is a slave which prepares food for fungi.