I. There Are Microbes in All Three Domains • While microbes are found just about
ID: 168637 • Letter: I
Question
I. There Are Microbes in All Three Domains
• While microbes are found just about everywhere, we tend not to think about them much because we cannot see them. Unlike other groups of organisms that are categorized by their evolutionary relatedness, the primary criterion that distinguishes microbes from other groups of organisms is __________________. •
Microbes are among some of the most evolutionarily successful organisms for the following reasons: 1. Microbes are genetically diverse. Approximately _______________ species of microbes are thought to exist.
2. Microbes can live in a diverse range of settings and can acquire nutrients from diverse sources. • Provide several examples of environments in which microbes can live. • What sorts of nutrients can microbes use to support their metabolic needs?
3. Microbes are abundant. Give a few examples of places microbes live in extremely high numbers.
• Bacteria are incredibly efficient in carrying out life’s functions. They require only the following structures to function. For each of these structures, indicate its role in the bacterial cell. Plasma membrane:
Ribosomes:
DNA:
Cytoplasm:
• In addition, there are several other optional structures that certain bacteria may possess. These include flagella, pilli, and capsules. Their functions include: o
Flagella:
Pilli:
Capsules:
A. Bacterial Reproduction
• One reason bacteria are so successful is that they can divide quickly. On average and in optimal conditions, bacteria can typically reproduce every _______________________.
• Binary fission, a form of ______________________ reproduction, results in genetically identical daughter cells. Mutation and gene transfer are the mechanisms used to initiate genetic diversity in bacterial populations.
• Bacterial genes are located on a circular chromosome. Unlike eukaryotic chromosomes, bacterial DNA lacks introns and is organized in a way such that genes with similar functions are near each other and can be regulated as a group.
• Some bacteria have additional loops of DNA called plasmids. These come in several varieties. Explain the functions of each.
Metabolic plasmids:
Resistance plasmids:
Virulence plasmids:
Now explain how each type of gene transfer works:
Conjugation:
Transformation:
Transduction:
B. Metabolic Diversity Among Bacteria
• Contrast the differences between each type of trophic category in bacteria:
Chemoorganotrophs:
Chemolithotrophs:
Photoautotrophs:
What role do cyanobacteria play in the Oxygen Revolution?
Microbe Domain Prokaryotic or eukaryotic? Bacteria Protists Viruses ArchaeaExplanation / Answer
3)Metabolic plasmids:Metabolic plasmidscarry genes involved in the production of metabolic enzymes.Metabolic plasmids (also called degradative plasmids) possess genes to code enzymes that degrade unusual substances such as toluene (aromatic compounds), pesticides (2, 4-dichloro- phenoxyacetic acid), and sugars (lactose).
Resistance plasmids: resistance plasmid is a small element outside the chromosome that carries DNA information that fights against antibiotic drugs. An example of aresistance plasmid is pBR322 which carries the genes for tetracycline and ampicillin resistance.
Virulence-plasmids:Virulence-plasmids confer pathogenesity on the host bacterium. They make the bacterium more pathogenic as the bacterium is better able to resist host defence or to produce toxins.
conjugation:conjugation is the transfer of genetic material between bacterial cells by direct cell-to-cell contact or by a bridge-like connection between two cells.
Transformation:transformation is the genetic alteration of a cell resulting from the direct uptake and incorporation of exogenous genetic material from its surroundings through the cell membranes.
Transduction:Transduction is the process by which foreign DNA is introduced into a cell by a virus or viral vector.
B.Metabolic diversity :It mainly refers to the different metabolic strategies that organisms have evolved to obtain energy. Metabolic pathways evolved among prokaryotes before eukaryotes arose as the result of their interaction and coevolution with changing physicochemical environmental conditions.
Chemoorganotrophs:Chemoorganotrophs are organisms which oxidize the chemical bonds in organic compounds as their energy source.Chemoorganotrophs also attain the carbon molecules that they need for cellular function from these organic compounds. The organic compounds that they oxidize include sugars (i.e. glucose), fats and proteins.
Chemolithotrophs:chemolithotrophs obtain their energy from reactions with inorganic salts.A chemolithotroph is able to use inorganic reduced compounds as a source of energy.This process is accomplished through oxidation and ATP synthesis. The majority of chemolithotrophs are able to fix carbon dioxide (CO2) through the Calvin cycle, a metabolic pathway in which carbon enters as CO2 and leaves as glucose. For some substrates, the cells must cull through large amounts of inorganic substrate to secure just a small amount of energy. This makes their metabolic process inefficient in many places and hinders them from thriving.This group of organisms includes sulfur oxidizers, nitrifying bacteria, iron oxidizers, and hydrogen oxidizers.
Photoautotrophs: organisms that carry out photosynthesis. Using energy from sunlight, carbon dioxide and water are converted into organic materials to be used in cellular functions such as biosynthesis and respiration.
role of cyanobacteria play in the Oxygen Revolution:Cyanobacteria belong to Earth's oldest organisms. They are still present today in oceans and waters and even in hot springs. By producing oxygen and evolving into multicellular forms, they played a key role in the emergence of organisms that breathe oxygen.Oceanic cyanobacteria, which evolved into multicellular forms more than 2.3 billion years ago are believed to have become the first microbes to produce oxygen by photosynthesis.GOEalso called oxygen revolution.. Before the GOE, any free oxygen they produced was chemically captured by dissolved iron or organic matter. The GOE was the point in time when these oxygen sinks became saturated, at which point oxygen, produced by the cyanobacteria, was free to escape into the atmosphere.