Lecture 2 Flashcards
Microbes make up what percent of the earths biomass?
around 60%
How many microbial species have been idetified?
less than 0.5% of around 2-4 billion
What microbes are acellular?
viruses and prions
What are prokaryotes microbes?
archaea and bacteria
What are eukaryotes microbes?
alae, fungi, protoza
What does the three-domain tree suggest?
eukaryotes are of archaeal origin
Why is the ring of life more representative?
eukaryotes have a mixed bacterial/archaeal lineages
How did eukaryotes arise?
when an archaeal host ingested a bacterium = mitochondria
What are the 4 characteristics of LUCA?
1) DNA as genetic material
2) Proteins and RNAs to catalyze essential processes needed to grow and reproduce
3) lipid membrane
4) lived in hydrothermal vents
How do we know where LUCA lived?
after isolating only the genes conserved between bacteria and archaea not shared by lateral gene transfer (355 genes). it was found that the function of these genes utilized hydrogen as an energy source and had reverse gyrase which is found in extremophiles.
Why can identifying LUCA help us identify life on other planets?
hydrothermal vents are common within our solar system
ex) icy moons like Europa and Enceladus have underground seas
What is the Taxonomic classification from most to least specific? eukarya
Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species
What is special about the taxonomic classification for prokaryotes
They have no kingdoms and that have a strain which is more specific than species
How do we classify prokaryotes
sequence variation in the 16S rRNA gene
The variable regions V1-V9 have high sequence divergence between species
What is the criteria for designating a new species?
a 16S rRNA gene sequence is less than 97% similar to another known species
Can most microbes be cultured in standard laboratory conditions?
nope
What is an enterotube II?
can determine species via sample/culture reacting with 12 different growth mediums
What is metagenomics?
can ID a species without culturing
it allow for sequencing of a gene
What sequences all of the DNA in a sample?
shotgun metagenomics
What is the largest of the prokaryotic domains?
bacteria
What is the largest bacterial phylum?
proteobacteria (1,300 species)
What is the ancestors of the modern chloroplasts?
cyanobacteria
Where does the name cyanobacteria come from?
from the bluish pigment phycocyanin ( phyco = algae (not actually an algae) and cyanin = blue-green )
How large are cyanobacteria?
very large (50 micron diameter
What is special about Filamentous Nostoc?
can fix nitrogen to organic nitrogen is heterocysts (hets) cells —anaerobic environment
Can nitrogen fixation occur in the presence of oxygen?
no
What are the 6 classes of proteobacteria?
alpha, beta, gamma, delta, epsilon, zeta
What are rhizobia?
alpha- proteobacteria that has a mutually beneficial relationship with leguminous plant. they fix atmospheric nitrogen. They invade root hair and form nodules on roots
What is the special enzyme rhizobia have that allow it to convert N2 into ammonia? How much ATP is needed?
nitrogenase
needs 16 ATP
What is gamma-proteobacterium enterohaemorrhagic E. coli (EHEC)?
bad and can be fatal bc it has a gene that encodes Shiga toxin severely damages the intestinal wall
—very very low infectious dose
What is agrobacterium?
soil alpha-proterobacteria that invades dicot/broadleaf plant. Injects t-DNA that causes a tumor to develop which does not kill the plant.
