Chapter #1 - The Evolutions Of Microorganisms and Microbiology Flashcards
Archaea
The domain of life containing anucleate cells that have unique lipids in their membranes, distinctive rRNA sequences, and cell walls that lack peptidoglycan.
Many are found in extreme environments, including those with high temperatures (thermophiles) and high concentrations of salt (extreme halophies).
Although some archae are members of a community of microbes involved in gum disease in humans, their role in causing disease hasn’t been clearly established.
Eukarya
The Domain of life that features organisms made of cells having a membrane-delimited nucleus and differing in many other ways from Archaea and Bacteria; includes protists, fungi, plants, and animals.
Fungi
A diverse group of eukaryotic microorganisms that range from unicellular to multicellular forms.
Molds and mushrooms are multicellular fungi that form thin, threadlike structures called hyphae.
They absorb nutrients from their environment, including the organic material molecules that they use as sources of carbon and energy.
Because of their metabolic capabilities, many fungi play beneficial roles, including making bread rise, producing antibiotics, and decomposing dead organisms. Other fungi cause plant and animal diseases.
Genome
The entire genetic makeup of an organism.
Genomic Analysis
An approach to studying organisms that involves sequencing the genome, identifying genes, and assigning functions to the genes.
Koch’s Postulates
A set of rules for proving that a specific microorganism causes a particular disease.
Still widely used, but their application at times is not feasible. When that is so, microbiologists sometime use molecular and genetic evidence.
Microbiology
The study of organisms that are usually too small to be seen with the naked eye; special techniques are required to isolate and grow them.
Microorganism
An organism that is too small to be seen clearly with the naked eye and lacks highly differentiated cells and distinct tissues.
Prions
Infectious agents, composed only of protein, that cause spongiform encephalopathies such as scrapie in sheep and “mad cow disease”.
Prokaryotic Cells
Cells having a type of structure characterized by the lack of a true, membrane-enclosed nucleus. All known members of Archaea and most members of Bacteria exhibit this type of cell structure.
Protists
Mostly unicellular eukaryotic organisms that lack cellular differentiation into tissues. Cell differentiation is limited to cells involved in sexual reproduction, alternate vegetative morphology, or resting states such as cysts.
Spontaneous Generation
An early belief, now discredited, that living organisms could develop from nonliving matter.
Viroids
Infectious agents of plants composed only of single-stranded RNA.
Viruses
Infectious agents having a simple acellular organization with a protein coat and a cucleic acid genome, lacking independent metabolism, and reproducing only within living host cells.
Simplest viruses composed of only proteins and a nucleic acid, and can be 10,000 times smaller than a bacterium.
Virusoids
Infectious agents composed only of single-stranded RNA. They are unable to replicate without the aid of specific viruses that coinfect the host cell. Cause some important human diseases.
Domains
The accepted sorting of organisms. Bacteria (sometimes referred to as true bacteria or eubacteria), Archaea (sometimes called archaeobacteria or archaebacteria), and Eukarya (all eukaryotic organisms).
Bacteria
The domain of life that contains anucleate cells having distinctive rRNA sequences and cell walls that contain the structural molecule peptidoglycan.
Usually single-celled. Most have cell walls that contain the structural molecule peptidoglycan.
Although most bacteria exhibit typical prokaryotic structure, a few members off the phylum Planctomycetes have their genetic material surrounded by a membrane.
Abundant in soil, water, and air, and are major inhabitants of our skin, mouth, and intestines. Some bacteria live in environments that have extreme temperatures, pH, or salinity.
Some bacteria cause disease, but many more play beneficial roles such as cycling elements in the biosphere, breaking down dead plant and animal material, and producing vitamins.
Enzymes
Catalytic proteins. They speed up the myriad of chemical reactions that occur in cells. They are the workhorses of the cell.
Tetrahymena
A protist that contained an RNA molecule that could cut out an internal section of itself and splice the remaining sections back together. Discovered by Thomas Cech in 1981.
Important discovery because at one point in evolution, there must have been a single molecule that could do both cellular work and replicate itself, the jobs of enzymes and DNA respectively.
Ribozymes
Catalytic RNA molecules. Can do both cellular work and replicate oneself.
RNA World
Coined by Walter Gilbert in 1986. Describes a stage in evolution when RNA was capable of storing, copying, and expressing genetic information, as well as catalyzing other chemical reactions.
However, for this precellular stage to proceed to the evolution of cellular life forms, a lipid membrane must have formed around the RNA. Easy to believe because lipids spontaneously from liposomes.
Liposomes
Lipids are major structural components of the membranes of modern organisms. They spontaneously form liposomes, vesicles bounded by a lipid bilayer.
RNA’s Function
Much of RNA exists in the ribosome, a structure that consists largely of rRNA and uses messenger RNA (mRNA) and transfer RNA (tRNA) to construct proteins. Also recall that rRNA itself catalyzes peptide bond formation during protein synthesis. RNA seems to be well poised for its importance in development of proteins.
ATP is a ribonucleotide and RNA can also regulate gene expression.
RNA Created DNA?
Because RNA and DNA are structurally similar, RNA could have given rise to double-standed DNA. It’s suggested once DNA evolved, it became the storage facility for genetic info because it provided a more chemically stable structure.