Brief Overview of Microorganisms

Pregunta	Respuesta
List some of the vital functions of microorganisms.	They maintain an aerobic atmosphere which supports aerobic life forms, they are the base of the food chain, they maintain water and soil quality, and they are vital in both the carbon and nitrogen cycles.
Name the microorganism groups that are not eukaryotes or prokaryotes.	Akaryotes - viruses and prion proteins.
What are algae?	Photosynthetic eukaryotic protists which all contain chlorophyll in the photosynthetic membrane of their subcellular chloroplast. They may be unicellular or multicellular and are differentiated from cyanobacteria by the absence of a peptidoglycan cell wall.
What is the general range of bacterial size?	0.1 - 1.5 um.
What is the main attribute of a cell that viruses lack?	The ability to replicate without a host.
What does a virus consist of?	A nucleic acid molecule (DNA or RNA) and a protein coat or 'capsid'.
What determines the specificity of a virus' interaction with its host cell?	The proteins, most frequently glycoproteins, in its capsid.
Which organisms do viruses infect?	A wide variety of animal and plant species, prokaryotes, and at least one eukaryotic alga and one protozoan.
How does a virus disturb cells it has infected?	It redirects the host's DNA replication enzymes in order to replicate itself. Sometimes genetic information from a virus is inserted into the host chromosome as DNA to be replicated, whereas in other instances the viral genetic information can serve as a basis for cellular manufacture and release copies of the virus.
How are prion proteins distinct from viruses?	They do not appear to contain nucleic acids.
List some detrimental effects of microorganisms.	Diseases and spoilage (the breakdown of organic material).
What is a mass of branching, interlacing filaments known as?	A fungal mycelium.
What is a coenocyte and what properties does this involve?	A coenocyte is a continuous mass of cytoplasm confined within a series of branching tubes, something made possible in a mycelium by the perforated cross walls which allow free passage of nuclei and cytoplasm.
What is a mycelial fungus more commonly known as?	A mould.
What are the four groups that fungi are subdivided into?	The zygomycetes, the ascomycetes, the basidiomycetes and the deuteromycetes.
Distinguish between a Gram-positive and a Gram-negative cell wall.	A Gram-positive bacterial cell wall has a thick layer of peptidoglycan, between 15 and 80nm thick, and a cytoplasmic membrane. A Gram-negative bacterial cell wall has a thin layer of peptidoglycan, ~2nm, a cytoplasmic membrane and an outer membrane also of ~8nm thickness.
List some properties of fungi that are beneficial to other organisms, and those specific to humans.	Their saprophytic nature decomposes organic matter and recycles nutrients to make them available to other organisms later in the food chain; their anaerobic nature means they produce CO2 and ethanol and so they are involved in the production of foods including bread and beer; they produce bioactive secondary metabolites such as antibiotics (e.g. penicillin) and immunosuppressive drugs (e.g. cylosporin) that are important in human and veterinary medicine.
What is an S-layer and what might its advantages be?	An S-layer is a lattice of protein or glycoprotein molecules of a single molecular species that may be present on Gram-positive and Gram-negative bacteria as well as archaea. It may protect the cell from wall-invading enzymes, from predatory bacteria and bacteriophages, and it may also be involved in maintaing cell shape and in cell adhesion to host epidermal surfaces.
Differentiate between the capsule and the glycocalyx.	The capsule is a condensed, well-defined layer of polysaccharide material surrounding a bacterial cell, whereas a glycocalyx is a loose meshwork of fibrils extending from the cell.
Give two reasons that microorganisms are the most prevalent living matter on earth.	They have a wide variety of survival techniques in a range of environments, and they reproduce rapidly.
Give an example of a Gram-negative and Gram-positive bacterium.	E. coli and S. aureus, respectively.
What are the two most common shapes of bacteria?	Bacilli and cocci.
Where is the largest human commensal microbe population found?	In the large intestine, predominately the caecum.
List some shapes of bacteria, other than bacillus and coccus.	Spirilla, spirochetes, helices, vibrio, flat and pleomorphic.
Although bacterial movement may appear random, what is usually the cause of their movements?	Chemoattractant gradients such as those for nutrients.
Despite not being membrane bound, prokaryotic DNA tends to exist in a particular area. What is this called?	The nucleoid.
How are slime moulds characterised?	By the presence of an amoeboid multinucleate mass of cytoplasm called a plasmodium at some point in their life cycle.
What shape is a slime mould in its vegetative state and when starved?	Amoeboid and slug-like, respectively.
What enables the plasmodium of a slime mould fruiting body to migrate?	The cytoplasm can flow in all directions in the coenocytic structure.
List some bacterial strategies for the generation of metabolic energy which allow them their range of niches.	Conversion of light energy to metabolic energy in the absence of O2, production of O2 in the absence of light, aerobic respiration, use of alternative electron acceptors to O2 including NO3-, SO4(2-) or CO2, and fermentation in which energy is derived by metabolic rearrangement of chemical growth substrates.
What is the significance of prokaryotic communities forming large consortia?	Protection from a threat by sheer numbers and the presence of a variant of any gene due to high cell number increases genetic diversity.
What is quorum sensing?	A form of communication used by many bacteria that involves the production of autoinducers or pheromones that are used to regulate the transcription of genes involved in diverse physiologic processes. These may include bioluminescence, plasmid conjugal transfer and the production of virulence determinants.
What distinguishes archaea from bacteria and what makes them similar?	Bacteria and archaea are indistinct based on morphology, size and microscopic structure but archaea do not possess a peptidoglycan cell wall (and so cannot be Gram-stained) and they have introns in their DNA and tend to live in extreme envoronments such as salt lakes or hot springs.
What microorganisms are included in the eukaryotes?	Algae, protozoa, fungi and slime moulds.
Which microorganisms are included in the prokaryotes?	Bacteria and archaea.
What are the protists subdivided into?	Algae, fungi, slime moulds and protozoa.
What are protozoa?	Unicellular non-photosynthetic protists that exist in flagellated, ciliated and amoeboid forms and have no cell wall.

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