Bacteria and Archaea Flashcards
microbe
organisms that cannot be seen with the naked eye (need a microscope)
prokaryote
a unicellular organisms that lack a nucleus and (generally) lacks organelles
three domains of life
bacteria
archaea
eukarya
last universal common ancestor (LUCA) traits
cells
central dogma
- DNA - RNA - proteins
- genetic code
adenosine triphosphate (ATP)
organic compounds with carbon-hydrogen bonds
bacteria
first classified in 1680s Antony van Leeuwenhoek
yet many species remain unclassified
wide variety of habitats and niches
oldest fossils are about 3.5 billion years old
Antony van Leeuwenhoek
he first classified bacteria in 1680s
father of microbiology
cyanobacteria
first organisms to perform “oxygen producing” photosynthesis
oldest fossils - 2.6 bya
signatures of oxygen in atmosphere - 2.3 to 2.1 by a
made aerobic respiration possible
archaea
first classified in 1977 by Carl Woese and George Fox
best known for living in extreme environments, but are found in a wide variety of habitats
oldest fossils are about 3.5 billion years old
Carl Woese and George Fox
first classified Archaea in 1977
phylogenetic trees based on ribosomal RNA sequences
Woese proposed the 3 domain system
bacteria and archaea diversity
only about 10,000 species of Bacteria and about 500 species of Archaea have been formally described
difficult to draw boundaries between species due to horizontal gene transfer
estimates of total species range from 1 million to 1 trillion
extremophiles
organisms that live in extreme environments
ways to characterize Bacteria and Archaea
enrichment culture
metagenomics or environmental sampling
enrichment culture
establish specific conditions
e.g. temperature, light, food, grow cells, isolate for further study
metagenomics or environmental sampling
has revealed lots of uncharacterized diversity
collect massive amounts of DNA or RNA sequences soils or water
detect species (genomic) or functional (expressed genes) diversity
abundance of Bacteria and Archaea
in terms of toal volume, Bacteria and Archaea are the dominant organisms of Earth
estimated 5x10^30
- chain longer than Milky Way!
- 50% of all carbon
- 90% of all nitrogen and phosphorus
- teaspoon of soil contains billions of cells
evolutionary rates of Bacteria and Archaea
reproduction is fast, thus they have short generation times
-E. coli cells divide in about 20 minutes at 37C
lateral gene transfer common, plus higher mutation rates than eukaryotes
-genetic diversity
implications for bacterial resistance and growth of “superbugs”
bacteria characteristics
most bacteria are about 1 micrometer in diameter, but some are much smaller
cell volume ranges from 0.15 micrometers^3 to 200 x 10^6 micrometers^3
-1.3 billion times the difference
new study in 2015: new bacteria as small as 0.009 micrometers^3
shape varies from rods to spheres to spirals
motility varies: some bacteria are nonmotile, but swimming and gliding are common
two general types distinguished by gram stain (detects peptidoglycan)
Achaea shapes
same rotes, spheres, spirals
also some that look like triangles or squares
reproduction
Bacteria and Archaea reproduce by (asexual) binary fission
- DNA uncoils and duplicates
- cell grows in size
- DNA copies move toward opposite poles
- new cell wall splits cel into two
genetic variation
mutation
gene transfer:
transformation
transduction
conjugation
different from sexual reproduction:
- one-way transfer
- transfers are limited to small number of genes
transformation
uptake of DNA from the environment
transduction
virus picks up and transfers DNA between cells
conjugation
direct transfer by cell-to-cell contact
metabolic diversity
bacteria and archaea domains are the dominant forms of life on Earth and are able to live in a wide variety of environments
much of this success is attributed to a wide diversity of metabolism
i.e. photo, chemo, hetero, auto…
photoautotrophs
energy from light
carbon from inorganic CO2
e.g. plants and algae; cyanobacteria, purple sulfur bacteria
chemoautotroph
energy from chemical reactions
carbon form inorganic CO2
only bacteria and archaea, many types
photoheterotroph
energy from light
carbon from organic molecules
only bacteria and archaea
e.g. purple non-sulfur, helicobacteria
chemoheterotrophs
energy and carbon from organic material
e.g. animals and fungi; many bacteria and archaea
decomposers
breakdown of dead organic matter
makes organic compounds available for other organisms
many have mutualistic relationships with plants and animals (mainly in gut)
nitrogen fixation
conversion of atmospheric nitrogen to forms that can be used by plants
nitrogen is often a limiting factor of plant growth
pathogenic bacteria
only a tiny fraction of bacteria are pathogenic (disease-causing)
Robert Koch
1843-1910
did a study of causative link between bacteria and disease
made Koch’s postulates
Koch’s postulates
microbe present in individuals with disease, absent from healthy individuals
microbe is isolated and grown in our culture
microbes from culture injected into animals produces symptoms of disease
microbe again isolated from diseased animal, should be same as original organism
microbiome
a community of microbes that share a particular space
human microbiome
lots of research on microbiome of human digestive tact
each person has about 100 different species (trillions of cells) of bacteria and archaea
analysis of gene expression supports physiological role including:
- digestion of complex carbohydrates
- synthesis of amino acids and vitamins
bioremediation
the use of organisms (usually Bacteria Archaea) to degrade environmental pollutants
pollutants often hydrophobic
- do not dissolve in water, accumulate in sediments
- can spread through food chain
microbiology
the study of organisms that can be seen only with the aid of microscope
germ theory of disease
states that infectious diseases are caused by specific microbes in the body
infectious diseases
are spread in 3 main ways:
- person to person
- by bites from insects or animals
- ingesting contaminated food or water, or from the surrounding environment
toxin
a poison
endospores
tough, thick-walled dormant structures formed during times of environmental stress, often in response to a lack of nutrients
contain a copy of the cell’s DNA, RNA, ribosomes, and essential enzymes that becomes surrounded by a tough resistant wall
resistant to high temps, UV radiation, and even antibiotics
when conditions become favorable, they resume growth as normal, actively dividing cells
bacteria
biofilms
dense bacterial colonies enmeshed in a polysaccharide-rich matriculates, which helps shield the bacteria from antibiotics
direct sequencing
a technique based on isolating and sequencing a specific gene from organisms found in a particular habitat
along with metagenomics/environmental sequencing
plasmid
a small circular piece of DNA
often contain accessory genes that aren’t required for normal growth, but can be advantageous
e.g. antibacterial resistance
gram-positive
a plasma membrane surrounded by a cell wall with extensive peptidoglycan
gram-negative
have a plasma membrane surrounded by a cell wall hat has two components:
-a thin gelatinous layer containing peptidoglycan and an outer phospholipid bilayer
shapes of bacteria
shape varies from rods to spheres to spirals
bacteria motility
motility varies: some bacteria are nonmotile, but swimming and gliding are common
