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