The Microbial World Flashcards
What are microorganisms?
- organisms and acellular entities too small to be clearly seen by the unaided eye (some exceptions)
- lack highly differentiated tissues
- often unicellular
- generally less than 1 mm in diameter
What is the difference between prokaryotic and eukaryotic microbial cells?
- prokaryotic cells lack a true membrane-bound nucleus and do not have membrane bound organelles (not absolute)
- eukaryotic cells have a membrane-bound nucleus and membrane bound organelles
- eukaryotes are more complex and are usually larger
How did microbes evolve and become so diverse?
mutation of genetic material -> new genotypes -> advantageous phenotypes -> natural selection
How are bacteria and archaea able to adapt more quickly?
- because they are haploid
- can increase genetic diversity by horizontal gene transfer within the same generation
What are 3 types of horizontal gene transfer and how do they differ?
- transformation: bacteria take up DNA from their environment
- conjugation: one bacterium sends a copy of a plasmid across a protein tube to another bacterium
- transduction: bacterial DNA packed into a virus that can infect another bacterium
In what order did organisms appear on Earth?
- origin of Earth (4.6 bya)
- origin of cellular life (4 bya)
- anoxygenic phototrophic bacteria
- origin of cyanobacteria
- modern eukaryotes (2 bya)
- algal diversity
- shelly invertebrates
- vascular plants
- mammals
- humans
What percentage of Earth’s history had microbial life forms only?
80%
Why are microorganisms important?
- oldest form of life
- most populous and diverse group of organisms
- major fraction of biomass and key reservoir of essential nutrients
- play a major role in recycling essential elements
- some can carry out photosynthesis
- influence all other living things (in a good or bad way)
- excellent tools for study
How do microorganisms affect humans?
- agriculture: help cows digest cellulose
- food: fermentation
- disease
- energy: ferment biofuels
- industry: antibiotics, enzymes
- human microflora: help our immune system and give us essential vitamins
- cycle nutrients: nitrogen
How was the Universal Phylogenetic Tree developed?
- three domain system based on a comparison of the DNA encoding small subunit ribosomal RNA
- divides microorganisms into bacteria, archaea, and eukarya
- isolate DNA from each organism
- make copies of rRNA from PCR
- sequence DNA
- analyze sequence (looking at evolutionary distance)
- generate phylogenetic tree
How are bacteria, archaea, and eukarya related?
- connect at LUCA (last common ancestor)
- archaea come off of the eukarya branch (more closely related DNA wise)
- bacteria: have peptidoglycan, no introns, and no histones
- archaea: no peptidoglycan, have some introns, and have histones
- eukarya: no peptidoglycan, have introns and histones
What is the prokaryotic “species”?
- bacteria and archaea do not reproduce sexually and are therefore not defined as an interbreeding natural population
- a microbial species is a collection of strains that share many stable properties and differ significantly from other groups of strains
What is a microbial strain?
- subset of microbial species
- descendants of a single, pure microbial culture
- one stain is designated as the type strain (permanent example, fully characterized, not necessarily the most representative)
- letter and # combo designates the strain
How are microbes named?
- genus and then species
- developed by Carl Linnaeus
ex: Escherichia coli, Bacillus subtilis, Micrococcus luteus
What did Robert Hooke do?
- coined the term cell
- described the fruiting structures of molds
