Unit 8 Flashcards
what is the purpose of microbes inhabiting plant tissues?
nutrient support for plants or pathogen protection
where does mutualism occur?
root nodules
what kind of plants do mutualism?
leguminous plants - legumes (soybeans, beans, peas)
what occurs for root module symbiosis?
association between legumes and N2 fixing bacteria
can legumes grow without nitrogen fertilizer?
yes
- reduces polluting effects of fertilizer runoff and saves money
what are microbes in symbiosis?
rhizobia
what do rhizobia do?
N2 fixing
- form large populations
- secrete rhicadhesin protein
- attach to root hairs
what do legumes do?
protect nitrogenase from oxygen
what is leghemoglobin?
oxygen buffer
what do the roots of leguminous plants secrete and what is the purpose?
- secrete organic compounds
- stimulate growth of diverse rhizosphere microbial community
what does parasitism in plants cause?
gal disease
what do Agrobacterium do?
form tumorous growth on diverse plants
Agrobacterium tumefaciens
crown gall disease
Agrobacterium rhizogenes
hairy root disease
what is Ti plasmid?
- trasnferred DNA (T-DNA)
- integrated into plant’s genome
what is the purpose of T-DNA?
genes for tumor formation and synthesis of modified amino acids called opines
what is the purpose of opines?
source of nutrients for A. tumefacien cells
what are modified Ti plasmids?
deleted disease genes
- keeps transfer genes
how to genes of interest get added to Ti plasmid?
genetic engineering
what are modified Ti plasmids used for?
construction of transgenic plants
mycorrhiza
plant + fungi interaction
what are the mutualisms between?
plant roots and fungi
are nutrients only transferred one way?
no
- both directions
- fungus transfer P and N from soil to the plant
- plant transfers carbs to fungus
what do microbes in mammals do?
help with digestion in mammalian gut
what do microogranisms have that help digest cellulose?
mammals lack enzymes to digest cellulose so they have genes that helps digestion of complex polysaccharides
what helps with digestion of polysaccharides?
- glycoside hydrolases
- polysaccharide lyases
what are ruminants?
herbivores that possess special digestive organs (rumen)
what are the dominant bacteria and archaea in rumen?
Firmicutes and Bacteroidetes
Methanogens
which microbe does not like cellulose and which animal does it not grown in?
Streptococcus bovis - not grow in grass-fed cows in large amounts
what does Streptococcus bovis love?
starch
- diet switched from grass to grains
what kind of bacteria is Streptococcus bovis?
lactic acid
- lactic acid acidifies rumen below normal pH
- acidification and inflammation of rumen
what do legume plants contain?
mimosine (amin-acid like)
what is mimosine converted to?
toxic compounds in rumen by existing microorganisms
what could Hawaii ruminants feed with?
legume
- they had bacteria that degraded toxic mimosine
what bacteria is inoculated with Hawaii ruminants?
Australiam ruminants
- restored ability to eat legume plants
what is the human microbiome?
microbes of whole human body
- role in human health
what did surveys of the human gut flora use?
16S rRNA gene sequencing and metagenomic analyses
similarities in individuals are evident at which taxonomic level?
phyla
what is found in a gut for those with low fiber diet?
bacteroidetes
what do Bacteroidetes do?
eat intestinal mucosa which develops ulcerative colitis
reduction of _________________ occurs
short chain fatty acids
what occurs with low fiber diet?
butyrate levels drop
G-protein coupled signaling and histone deacetylase
- causes cancer, obesity and diseases
how to study microbiomes?
- feed people different foods
- collect fecal matter
- analyze samples
- determine any changes
- infected cultures with intestinal microbiota
- determine how they colonize cells and type of inflammatory response
how to solve Clostridium difficile?
transplant patients with fecal material form healthy person
- fecal in tablet form, use metagenomics and sequence microbiome to analyze, improvements made
termites
special group of insects that established symbiotic association with protists and bacteria that degrade lignocellulose
what occurs in insects’ gut?
fix N and participate in carbon metabolism
what are dominant in insects’ gut?
methanogens and acetogens
what is Hawaiian bobtail squid?
small marine invertebrate
what colonizes squid?
Aliivibrio fischeri
what is Aliivibrio?
light organs
- luciferase in bacteria that emits light upon induction with AHL quorum sensing molecules
what is produced by squid to kill bacteria?
nitric oxide
what happens after A. fischeri colonizes the light organ?
no levels diminish rapidly
how does A.fischeri enter squid?
ciliated ducts
biofilms
- assemblages of bacterial cells attached to surface and enclosed in an adhesive matrix that is product of excretion by cells and cell death
- matrix is mixture of polysaccharides, proteins and nucleic acids that bind cells together
what do biofilms do?
trap nutrients for microbial growth and help prevent detachment of cells on dynamic surfaces
what are biofilm highly tolerant to?
antibiotics and stressors
microbes in biofilms
- extracellular matrix genes for stress tolerance
- express genes for enzymes that promote biofilms (attached) mode of life
diguanylate cyclase
enzyme that creates c-di GMP (cyclic guanosine monophosphate)
what does c-di-GMP do?
binds to transcriptional regulators and promotes biofilms formation
c-di-GMP binding proteins
- reduce activity of flagellar motor
- regulate cell surface proteins required for attachment
- mediates biosynthesis of extracellular matrix polysaccharides
Pseudomonas aeruginosa
- cystic fibrosis
- famous biofilm former
- AHL: intracellular inducer
what does AHL do?
turns on gene DGC
- increased c-di GMP levels
what does elevated c-di-GMP levels initiate?
the production of extracellular polysaccharide and decrease flagellar function
why bacteria forms biofilms?
- self-defence: biofilms microbes are resistnat to physical and chemical stressors
- attachment to favorable niche: specific structures on biofilms help microbe to remain attached to nutrient rich surfaces
- close association with kins: more opportunities for nutrients and genetic exchange
mineral recovery and acid mine drainage
- extract valuable metals from low-grade ores
- ores have energy reservoirs for microbes: FeS2, metal-HS complexes
- concentration of metal in ore is low
what bacteria is used for metal leaching in ores?
Acidithiobacillus ferrooxidans
- acidophallic iron oxidizer
what does Acidithiobacillus ferrooxidans oxidize?
- arsenopyrite and release Au
- uranium with O2 available (U4+ to U6+)
- O2 reduced to H2O
bioremediation
- microbial cleanup of oil, toxic chemicals, or other enviro pollutants by stimulating activities’ of hydrocarbon-degrading microogranisms
what are pollutants?
natural materials
xenobiotic chemicals
what is the most successful process for cleaning up spills of crude oil or leakage of hydrocarbons from bulk storage tanks?
bioremedition
what does oil-oxidizing bacteria do?
- grows rapidly
- supplies inorganic nutrients and oxygen
what compounds can be oxidized rapidly?
non-volatile oil compounds
what are not preferred microbial substrates?
- branches chain and polycyclic hydrocarbons
what happened with the accident in Mexico?
- 35% of resulting hydrocarbons were comprised of low-molecular-weight components and natural gas
- development of bacteria that can oxidize easily degraded and more recalcitrant hydrocarbon components
what is bioremediation of pesticides?
oxidation via microorganisms for energy extraction
what microbe dechlorinates pesticide aerobically?
Burkholderia
what occurs dechlorination?
oxygenase breaks down aromatic ring and introduces compound into TCA cycle
what are plastics examples of?
xenobiotics
what microbe breaks down and consume PET as carbon and energy source?
Ideonella sakaiensis
what are the wastewater treatments?
physical and chemical methods
microbial treatment
what does the pretreatment of wastewater involve?
- mechanical processes to remove large debris and inorganic matter in water sample
- remove highly toxic substances
what is the secondary treatment processes?
- series of degradative and fermentative reactions carried out by various prokaryotes under anoxic conditions
- soluble components are fermented to yield mixture of fatty acids, H2 and CO2
- then discharged into rivers and streams
what does potable water require?
further treatment to remove pathogens
- filtration, chlorination and UV
microbially influenced corrosion
metal corrosion by SRB
- use sulfate as TEA and produce H2S
- H2S is corrosive
- H2 and Fe0 are donor
what is the MIC microbe?
Desulfopila corrodens
