Viral Microbiology and Baltimore Classification

The Baltimore Classification system categorizes viruses based on their method of producing mRNA, the messenger RNA that carries genetic information from DNA to ribosomes for protein synthesis.

<p>Class I</p> Signup and view all the answers

<p>Class IV</p> Signup and view all the answers

<p>The Baltimore Classification system is based on how viruses produce mRNA, while viral taxonomy relies on sequence-based relationships.</p> Signup and view all the answers

<p>False</p> Signup and view all the answers

<p>Rolling circle replication begins with a nick in the positive strand of the double-stranded replicative form (dsDNA). The negative strand is then used as a template to extend the positive strand. Once replication is complete, the original positive strand is cleaved and joined to the newly synthesized strand, resulting in the replication of the viral genome.</p> Signup and view all the answers

<p>The viral genome integrates into the host genome.</p> Signup and view all the answers

<p>False</p> Signup and view all the answers

<p>Lambda phage integrates into the host genome by using a specific site on its DNA called an attachment site (att) that recognizes and binds to a corresponding site (att) on the bacterial chromosome.</p> Signup and view all the answers

<p>They are transcribed into mRNA for protein synthesis.</p> Signup and view all the answers

<p>False</p> Signup and view all the answers

<p>Retroviruses, such as HIV, are unique in their ability to convert their RNA genome into a double-stranded DNA copy using reverse transcriptase. This DNA copy can then integrate into the host genome, becoming a provirus and replicating with the host cell.</p> Signup and view all the answers

<p>The viral shunt refers to the process by which viruses cause the lysis of microorganisms, releasing dissolved organic matter (DOM) and particulate organic matter (POM) into the environment. These organic materials are then taken up by other microorganisms, leading to a cycling of carbon and nutrients within the system.</p> Signup and view all the answers

<p>Auxillary Metabolic Genes (AMGs) refer to genes encoded by viruses that can enhance the metabolic functions of their host organism. For example, some cyanophages encode the psbA gene, which produces a subunit of photosystem II in the host cyanobacteria, increasing their photosynthetic efficiency.</p> Signup and view all the answers

<p>Gene Transfer Agents (GTAs) are virus-like particles that play a role in the transfer of genetic material between different species. They are closely related to viruses as they involve incorporating their genome into a host, replicating it, and then producing and releasing progeny particles.</p> Signup and view all the answers

<p>Microbial ecology investigates the complex interactions between microorganisms and their environments, including both abiotic factors like temperature and nutrient availability and biotic factors, such as other microbial species.</p> Signup and view all the answers

<p>Studying microbial ecology is crucial because the vast majority of microorganisms (estimated at 99%) cannot be cultured in the lab using conventional methods due to the Great Plate Count Anomaly. This means we are unable to fully understand microbial communities using solely lab cultures and need to utilize advanced techniques like molecular methods and environmental sampling to explore their diversity and interactions.</p> Signup and view all the answers

<p>Microbial richness refers to the number of different species present in a particular ecosystem, while microbial abundance refers to the proportion of each species within that community. Richness describes the diversity of species, while abundance reflects the relative dominance of each species.</p> Signup and view all the answers

<p>Temperature</p> Signup and view all the answers

<p>Microbial cooperation benefits a community when microorganisms share metabolic products or genetic information that allows them to thrive in situations where they would not succeed alone. For instance, one species may produce a nutrient that is essential for the growth of another, or they may share genes involved in breaking down complex compounds.</p> Signup and view all the answers

<p>Microbial competition impacts community composition by influencing the relative abundance of different species. When different species compete for the same limited resources, such as nutrients or space, one or more species may become dominant while others decline, leading to changes in the community's makeup.</p> Signup and view all the answers

<p>Microbial predation occurs when one microorganism hunts or disrupts another microorganism to obtain nutrients or resources. This can involve attacking, consuming, or releasing toxins to harm the prey organism.</p> Signup and view all the answers

<p>Chemical profiling</p> Signup and view all the answers

<p>This mutualistic relationship involves the alga <em>Chlamydomonas reinhardtii</em> providing carbon, a vital nutrient for the bacterium, while <em>Mesorhizobium sangaii</em> supplies fixed nitrogen, essential for the alga's growth and development.</p> Signup and view all the answers

<p>The human body provides various microenvironments each with distinct conditions for growth and development, These are all areas where conditions are altered to meet the needs of microbes.</p> Signup and view all the answers

<p>Microbial communities vary in their composition and diversity based on a number of key factors, including available nutrients, oxygen concentrations, pH levels, temperature, and competition between different species.</p> Signup and view all the answers

<p>The human gut exhibits distinct oxygen and pH gradients. The lumen, the innermost part of the gut, is predominantly anaerobic with low oxygen concentration and pH levels of approximately 7. However, the epithelial layer closer to the intestinal wall can experience a higher oxygen concentration.</p> Signup and view all the answers

<p><em>Bacteroides spp.</em> are specialized for the gut with the ability to break down polysaccharides, both from the diet and the mucosal layer, producing beneficial short-chain fatty acids. They are also capable of respiring oxygen, allowing them to exist in the slightly more oxygen-rich environment near the epithelial layer.</p> Signup and view all the answers

<p>One example is the cross-feeding interaction between <em>Bacteroides spp.</em> and other gut bacteria like <em>E. coli</em>, <em>S. enterica,</em> and <em>C. difficile</em>. <em>Bacteroides spp.</em> provide simpler sugars and carboxylic acids to activate these other bacteria. Another example is the production of the C capsule by Bacteroides spp., which gets recognized by the host B cells and stimulates a positive immune response.</p> Signup and view all the answers

<p>Exposure-Adherence-Invasion-Multiplication</p> Signup and view all the answers

<p>False</p> Signup and view all the answers

<p>The virulence of a pathogen is commonly measured using the LD50 (Lethal Dose 50) assay. This involves determining the number of microbial cells necessary to kill 50% of a test population.</p> Signup and view all the answers

<p>Virulence factors are molecules or mechanisms produced by bacteria or viruses that enhance their ability to cause disease. These factors can involve toxins, enzymes, capsules, or other specialized structures. An example of a virulence factor is the AB toxin produced by <em>Vibrio cholerae</em>, which causes severe diarrhea in infected individuals.</p> Signup and view all the answers

<p><em>Pseudomonas aeruginosa</em> is a facultative anaerobe capable of utilizing oxygen or nitrate as an electron acceptor for energy production. It can use various sugars as carbon sources and is adept at colonizing the human respiratory system, often leading to chronic infections. It employs Type IV Pili and Type III Secretion Systems to attach to and invade host cells, respectively, and produces a variety of virulence factors, including toxins and enzymes, contributing to its pathogenic potential.</p> Signup and view all the answers

<p>In cystic fibrosis patients, <em>Pseudomonas aeruginosa</em> and <em>Staphylococcus aureus</em> often coexist in biofilms. They have a complex interplay that prevents them from becoming spatially adjacent. <em>Pseudomonas aeruginosa</em> produces molecules like cyanide and pyocyanin, which inhibit <em>Staphylococcus aureus</em>, while <em>Staphylococcus aureus</em> produces acetoin, acetate, and peptides that are bactericidal to <em>Pseudomonas aeruginosa</em>. This antagonistic relationship shapes the structure and function of the biofilms in cystic fibrosis patients.</p> Signup and view all the answers

<p>Symbiosis refers to a cooperative interaction between two different organisms where both partners benefit. This partnership can be mutualistic, where both partners gain a clear advantage, or commensalistic, where one benefits while the other is neither harmed nor benefited. In contrast to parasitism, where one organism benefits at the expense of the other, in symbiosis, both partners ultimately thrive due to their collaborative relationship.</p> Signup and view all the answers

<p>Lichens are fascinating symbioses between fungi and photosynthetic microorganisms, either algae or cyanobacteria. The algae or cyanobacteria provide fixed carbon via photosynthesis, which is essential for the fungus's growth. The fungus, in return, provides shelter, protection from desiccation and nutrient uptake capabilities, enabling the symbiotic partnership to flourish.</p> Signup and view all the answers

<p>ANME and SRB exhibit an obligate syntrophic relationship in marine sediments, particularly those rich in methane. ANME oxidizes methane, which under normal conditions is energetically unfavorable. However, they couple this reaction with SRB that performs sulfate reduction, a highly favorable reaction. This energy transfer fuels the ANME's metabolism while SRB receives electrons for their sulfate reduction process.</p> Signup and view all the answers

<p>Metagenomics</p> Signup and view all the answers

<p>Leguminous plants form a close symbiotic relationship with nitrogen-fixing bacteria, primarily from the genera <em>Rhizobium</em> and <em>Bradyrhizobium</em>. The bacteria possess the enzyme nitrogenase, which can convert atmospheric nitrogen into a biologically usable form, ammonia. This newly fixed nitrogen is crucial for the plant's growth and development. In exchange for fixing nitrogen, the bacteria receive a safe and nutrient-rich environment within root nodules of the plant.</p> Signup and view all the answers

<p>The formation of root nodules in legumes is a complex process that begins with the recognition of the appropriate partner. Nod factors, oligosaccharide signaling molecules secreted by the bacteria, play a critical role in this early stage. These factors bind to receptors on the plant root hair and trigger a series of developmental changes. The bacteria then invade the root hair and form a specialized structure known as an infection thread. This thread acts as a pathway for the bacteria to move to the central root, where they eventually form the characteristic nodules. The nodules are specialized structures where the bacteria differentiate into bacteroids, which are adapted for nitrogen fixation. The Myc factors regulate these events, as well as the further development of the nodules.</p> Signup and view all the answers

<p>This tripartite symbiosis involves a host mealybug, an endosymbiont <em>Candidatus Trembalaya phenacola</em>, and a secondary symbiotic bacterium <em>Candidatus Trabutinella endobia</em>. <em>Candidatus Trembalaya phenacola</em> lacks genes for producing peptidoglycan, the structural component of bacterial cell walls, while <em>Candidatus Trabutinella endobia</em> lacks essential genes for amino acid synthesis. The mealybug contributes genes that enable the synthesis of peptidoglycan on the surface of <em>Candidatus Trembalaya phenacola</em>. The two endosymbionts then complement each other's metabolic functions, resulting in a cooperative relationship that benefits all three partners.</p> Signup and view all the answers

<p>Endosymbiotic bacteria, such as <em>Sodalis</em>, experience notable genomic alterations compared to their free-living counterparts. These include a reduction in genome size, indicative of streamlining their metabolic capabilities to rely on their host for essential functions. They also exhibit a pronounced bias toward A+T bases, which is associated with increased genome stability, potentially due to reduced selection pressure for adaptive mutations within the stable endosymbiotic environment.</p> Signup and view all the answers

<p>Soil is a complex mixture of inorganic and organic components. It typically consists of about 40% inorganic mineral matter, such as silica and sand, 5% organic matter, including decomposed plant and animal material, 50% air and water, and 5% microorganisms, including bacteria, fungi, protozoa, and nematodes.</p> Signup and view all the answers

<p>Soil is classified based on particle size into three main categories: sand, silt, and clay. Sand has the largest particle size (0.1-2 mm), silt is intermediate (0.002-0.1 mm), and clay has the smallest particle size (less than 0.002 mm). The proportions of sand, silt, and clay determine the soil's texture and properties, such as drainage, water retention, and nutrient availability.</p> Signup and view all the answers