Quiz Mikrobiologi 1 Virus, Bakteri, Actinomycetes

Viruses are considered simple because they lack the complex cellular structures found in other organisms. They are acellular because they do not have cells of their own and instead rely on host cells to reproduce. Viruses are also infectious agents because they have the ability to enter host cells and hijack their machinery to replicate and spread.

Archaea, a group of microorganisms, have unique adaptations that allow them to thrive in extreme environments. These adaptations include special structures, chemical compositions, and metabolic processes. These enable archaea to survive and grow in harsh conditions such as high temperatures, high salinity, acidic or alkaline environments, and high pressure. These adaptations make archaea distinct from other bacterial groups, which may not possess the same abilities to survive in extreme environments.

Archaea are able to grow in a variety of extreme environments, including anaerobic conditions (without oxygen), hypersaline environments (with high salt concentrations), extremely hot temperatures, and extremely cold temperatures. This adaptability allows archaea to thrive in habitats that are inhospitable to most other organisms.

Actinomycetes are a group of bacteria that are known for producing a wide range of antibiotics. These antibiotics have been used in medicine for many years to treat various bacterial infections. Due to their ability to produce these antibiotics, actinomycetes are considered the primary source of antibiotics used in medicine. Therefore, the statement that actinomycetes are the primary source of antibiotics we use in medicine is true.

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Viruses cannot reproduce independently from the host cell. They are obligate intracellular parasites, meaning they require a host cell to replicate and produce new virus particles. Once inside a host cell, the virus hijacks the cell's machinery to produce copies of itself. Without a host cell, viruses are unable to replicate and survive. Therefore, the correct answer is False.

The causative agent for cholera in humans is a member of the genus Vibrio. Cholera is caused by the bacterium Vibrio cholerae, which is transmitted through contaminated water or food. Vibrio cholerae produces a toxin that causes severe diarrhea and dehydration in infected individuals. This bacterium is specifically adapted to survive in aquatic environments and can multiply rapidly in conditions with poor sanitation. Therefore, Vibrio is the correct genus responsible for causing cholera in humans.

The G + C content of organisms is true because it can be easily determined, making it a useful tool for taxonomic classification. Additionally, the G + C content indirectly reflects the base sequence of the organism, providing information about its genetic composition. Therefore, all of these statements are true about the G + C content of organisms.

In the animal virus cycle, the first step is adsorption to the host cell surface. This refers to the attachment of the virus to specific receptors on the surface of the host cell. This initial interaction is crucial for the virus to gain entry into the cell and begin the infection process. Once the virus has attached to the host cell, it can then proceed to penetrate the cell and uncoat its genetic material, leading to the replication and production of new virus particles.

All of the options listed (the green bacteria, the purple bacteria, and the cyanobacteria) are groups of photosynthetic bacteria. Therefore, none of them can be considered as not a group of photosynthetic bacteria.

Rhizobium is the correct answer because it is a genus of bacteria that form a symbiotic relationship with legumes. These bacteria infect the roots of legumes and form nodules, where they convert atmospheric nitrogen into a form that can be used by the plant. This process, known as nitrogen fixation, benefits both the bacteria and the plant. Agrobacterium, Pseudomonas, and Bacteroides are not known to form nitrogen-fixing symbiotic relationships with legumes.

Pseudomonads are a large group of bacteria that are capable of spoiling refrigerated food and causing disease. They are known for their ability to grow and multiply in low temperatures, making them a common cause of food spoilage in refrigerated environments. Additionally, some strains of pseudomonads are opportunistic pathogens, meaning they can cause infections in individuals with weakened immune systems or compromised health. Therefore, the correct answer is "a and b."

Localized areas of cellular destruction and lysis caused by virus infection are called viral cytopathic effects (CPEs). Viruses can cause damage to host cells by directly killing them or by inducing changes in their structure and function. These effects can include cell rounding, cell detachment, cell fusion, and the formation of syncytia. Viral CPEs are important in the diagnosis of viral infections and can help identify the specific virus causing the damage.

Spirochetes are a group of bacteria that are responsible for causing various diseases. Syphilis is a sexually transmitted infection caused by the spirochete bacterium Treponema pallidum, while Lyme disease is caused by the spirochete bacterium Borrelia burgdorferi, which is transmitted through tick bites. Therefore, the correct answer is that spirochetes include the causative agents for both syphilis and Lyme disease.

Deinococci are known for their exceptional resistance to both radiation and desiccation. This means that they can survive and remain viable even in extremely dry conditions and in the presence of high levels of radiation. This unique characteristic sets them apart from other gram-positive cocci and rods, making them highly adaptable to harsh environments.

Proteobacteria are gram-negative bacteria that have significant importance as disease agents, nitrogen fixers, and major experimental organisms. This means that they can cause diseases in humans and other organisms, play a crucial role in converting atmospheric nitrogen into a form that can be used by plants, and are widely used in research and experimentation. Therefore, the correct answer is "all of these" as Proteobacteria fulfill all these roles.

Viruses may harm their host cells by hijacking the cellular machinery and resources for their own replication and survival. They can disrupt normal cellular processes, cause cell death, and induce immune responses, leading to tissue damage and disease. Additionally, viruses can manipulate host cell signaling pathways, interfere with gene expression, and evade the immune system, further contributing to cell damage and disease progression.

Helicobacter pylori is a bacterium that infects the stomach lining and is known to be a major cause of peptic ulcer disease. It is able to survive in the acidic environment of the stomach and can cause inflammation and damage to the protective lining of the stomach and duodenum, leading to the formation of ulcers. This bacterium is not responsible for gastroenteritis, cholera, or bacterial dysentery, which are caused by different pathogens.