Microbiology Chapter 4 Prokaryotes

The statement "Uncapsulated bacteria are the most dangerous" is false. While uncapsulated bacteria can still be harmful, encapsulated bacteria have an additional layer of protection that allows them to evade the immune system and cause more severe infections. Therefore, encapsulated bacteria are generally considered to be more dangerous than uncapsulated bacteria.

The bacterial cell wall does not play a role in locomotion for most of the cell. Locomotion in bacteria is primarily achieved through the use of flagella, which are long whip-like appendages that rotate and propel the cell forward. The cell wall, on the other hand, provides structural support and helps maintain the shape of the cell. It also serves as a platform for the attachment of surface appendages such as pili and fimbriae. Additionally, the cell wall helps counteract the effects of osmotic pressure by preventing the cell from bursting or collapsing. However, it does not have any direct involvement in locomotion.

The gram positive cell wall is not comprised of a low percentage of peptidoglycans. In fact, it consists of many polymer layers of peptidoglycan connected by amino acid bridges. Peptidoglycan is a major component of the cell wall in gram positive bacteria and provides strength and rigidity to the cell wall structure. Therefore, the statement that the gram positive cell wall has a low percentage of peptidoglycans is not true.

Short attachment pili are called fimbriae. Fimbriae are hair-like structures found on the surface of some bacteria that help them attach to surfaces. They are shorter than the longer, thicker pili called sex pili, which are involved in bacterial conjugation. Flagella, on the other hand, are whip-like structures that bacteria use for movement. Vegetative cells refer to the actively growing and dividing cells of bacteria.

Germination refers to the process by which a seed or spore begins to grow and develop into a new plant or organism. In the context of the question, the term "conversion back to a vegetative cell" suggests a transformation from a dormant state to an active state of growth. Germination is the most appropriate term to describe this process, as it specifically relates to the revival and growth of a plant or organism from a dormant state.

The correct answer is the Lipopolysaccharide layer (LPS layer). In gram-negative cell walls, the LPS layer is located adjacent to the exterior peptidoglycan layer. The LPS layer is composed of lipid A, core polysaccharide, and O antigen. It acts as a barrier, protecting the cell from harmful substances and contributing to the structural integrity of the cell wall. Additionally, the LPS layer plays a role in the immune response and can elicit an inflammatory response in host organisms.

The strong spore coat contributes to an endospore's resistance and is composed of highly crosslinked Keratin. This coat provides protection against harsh environmental conditions such as heat, radiation, and chemicals. The crosslinked Keratin makes the spore coat tough and resistant, preventing the entry of harmful substances and ensuring the survival of the endospore in unfavorable conditions.

The periplasmic space is the correct answer because it is the region that separates the outer plasma membrane from the peptidoglycan layer in gram-negative cell walls. This space is located between the inner and outer membranes of the cell and contains various proteins, enzymes, and other molecules. It plays a crucial role in the transport of nutrients, the degradation of harmful substances, and the maintenance of cell structure and integrity.

Lipid A is the toxic substance found in the lipid portion of the LPS layer. LPS, or lipopolysaccharide, is a component of the outer membrane of Gram-negative bacteria. It consists of three parts: lipid A, a core oligosaccharide, and an O antigen. Lipid A is responsible for the toxic effects of LPS, including the activation of the immune system and the induction of inflammation. It is recognized by the immune system as a danger signal and can trigger a strong immune response.

Bacillus megaterium is an example of a central endospore because it is a species of bacteria that forms endospores, which are dormant structures that allow the bacteria to survive in unfavorable conditions. In central endospores, the endospore is located in the center of the bacterial cell. Bacillus megaterium is known for its ability to produce large, heat-resistant endospores, making it a suitable example for this type of spore formation.

The correct answer is B and C because both Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) can be used to see the structure of viruses. SEM uses a beam of electrons to create a detailed 3D image of the virus's surface, while TEM uses a beam of electrons to create a detailed 2D image of the virus's internal structure.

Gram-negative bacteria are known to have a thin peptidoglycan layer, which is a characteristic feature of their cell wall. This makes them less susceptible to the action of penicillin and streptomycin, which primarily target the peptidoglycan layer. Therefore, it is not true that gram-negative bacteria have a high susceptibility to penicillin and streptomycin.

Dipicolinic acid (DPA) is thought to lend to the high resistance of endospores. DPA is a chemical produced by endospores that helps protect their DNA from damage and allows them to survive in harsh conditions. It forms complexes with calcium ions, which stabilizes the DNA and prevents it from being degraded. This, in turn, contributes to the spore's ability to withstand extreme temperatures, radiation, and chemical exposure.

The poliovirus is the smallest virus among the options given. It is a single-stranded RNA virus belonging to the family Picornaviridae. Poliovirus is responsible for causing polio, a highly infectious disease that primarily affects young children. It is transmitted through contaminated food and water, and can lead to paralysis or even death. The small size of the poliovirus allows it to easily penetrate the cells of the human body and cause infection.

The statement "the flagella is complex and consist of multiple microtubules" is not true about prokaryotes. Prokaryotes have a simpler structure for their flagella, which is made up of a single protein called flagellin. Unlike eukaryotes, prokaryotes do not have microtubules in their flagella. Instead, their flagella rotate in a whip-like motion, allowing the prokaryote to move.

Small acid-soluble proteins (SASPS) protect the DNA of the spore cell from UV radiation, dessication, and dry heat. These proteins bind tightly to the DNA molecule, forming a protective complex that shields it from damage caused by these harsh environmental conditions. This protective mechanism allows the spore cell to survive in extreme conditions and ensures the preservation of its genetic material until more favorable conditions are encountered.

Pleomorphism refers to the appearance of two or more distinctly different forms in the life cycle of some organisms. This means that these organisms can exhibit different forms or structures at different stages of their life cycle. It is a phenomenon commonly observed in certain microorganisms, such as bacteria and fungi, where they can switch between different forms depending on environmental conditions or other factors. Pleomorphism is not related to transformation, staining, or germination, which are different processes or phenomena in biology.

A lophotrichous bacterium is one that has a tuft of flagella at one or both ends of the cell. Among the given options, Spirillum volutans is the only bacterium that is lophotrichous. This means that it has a cluster of flagella at one or both ends, allowing it to move efficiently through its environment. The other options do not possess this characteristic, making Spirillum volutans the correct answer.

Eukaryotes have larger size 80S ribosomes located in the cytoplasm, not in organelles. The ribosomes in eukaryotes are responsible for protein synthesis and can be found freely in the cytoplasm or attached to the endoplasmic reticulum. Organelles such as mitochondria and chloroplasts have their own smaller ribosomes called 70S ribosomes. Therefore, the statement that eukaryotes have larger size 80S ribosomes located in organelles is not true.

Gram positive bacteria are not resistant to ionic detergents, sodium azide, and drying. Gram positive bacteria have a thick peptidoglycan layer in their cell wall, which retains the crystal violet stain during the Gram staining process, giving them a purple color. This thick peptidoglycan layer also makes them more susceptible to the action of detergents, sodium azide, and drying, as these agents can disrupt the cell wall and lead to cell lysis. Therefore, the statement that gram positive bacteria are resistant to ionic detergents, sodium azide, and drying is false.