MICROORGANISMS IN TERRESTRIAL ECOSYSTEM

bacteria
archea
fungi
protozoa

Bacteria

aerobic(70%)
anaerobic(14%)
filamentous(13%)

location

surface of soilparticle, water & nutrient

role

cycling and transformation of C,N,P,Fe,S of soil

cyanobac(soil bare)

convert N2 to N

functional groups

decomposers

Mutualists

Pathogens

Lithotrophs or
chemoautotrophs

Fungi

functions

decomposers

mutualists

pathogens/parasites

microorganismassociates
w/ vascular plant

commensalistic r/ship with palnt

mutualistic

pathogenic and harms the host

molecular signalling-two way comm

microbe plant i'reactions

epiphytes

live on surface of plants

endophytes

colonize internal plant tissue

live in aboveground

inhabit below ground plant tissue

Phyllosphere Microorganisms

phyllosphere

aerial surfaces of plant

SSU rRNA analysis

Rhizosphere & Rhizoplane

vol of soil around root influenced by
materials released from root

surface of root

Subtopic

Roles of microbes

labile source of nutrients

creating microbial loop

synthesis & degradation of OM

promotion of plant growth

associative nitrogen fixation

Mycorrhizae

mutualistic fungus-plant

colonize plany roots

associations

endomycorrhizae

enter root hairs

ectomycorrhizae

remain extracellular, form sheath (hyphae)

form by ascomycete & basidomycete

Arbuscular

found associating w/ crop n tropical plant

provide host w/ protection

trnasfer phosphorus to roots

provide ammonium to host

Agrobacterium
tumefaciens

causes crown gall disease

genes for plant infection

infected through wound

two components signal transduction

T DNA

Protozoa

role

predators of soil bacteria

feeding

on bacteria
other protozoa
soluble OM
fungi

functions

mineralizing nutrients

regulating bacteria populations

food source

Virus

many viruses infect plants

eg:TMV

wide range of virus

eg:TMV

one virus of note infects fungus

causes chestnut blight

to control fungal pathogen

community genome size

reflects genomic diversity in soil sample

no can be very high

Surfaces

smooth

hard for adhere

clay

contain minerals; kaolinite

Water

Thin water films

O2 higher & easy replenish

aerobic(outside)
anaerobic (inside)

depend on

rainfall

particle size

drainage

Temperature

composition of soil microflora

depends on

latitude and altitude

depth

pH

bacteria ( pH 6-8)

molds (pH acidic)

influence by

microbial metabolic activity

time of the year

climate

prev cropping history

Soil atmosphere

well-drained soil

influnce by soil particle size

rocks and soil

different organic and inorganic components

influence by:

weathering rocks

decomposition of plants

redistribution of materials
by water movement

very complex,
variety of habitat

soil particles

pore space

critical movement
of water & gas

optimum enviroment
for microbial growth

composition

topsoil

Humus
Minerals
Soil microbes
Plant roots

Subsoil

Fine particles
Minerals

Parent
Material

Weathered rock
Inorganic material

Bedrock

Unweathered
rock

Categories

Mineral

<20% organic C

Organic

at least 20% organic C

SOM

Importance

retains nutrients

maintain soil structure

hold water

level change depends
on environmental change

Production

release of CO2,
biomass production

small fraction becomes SOM

easily degraded comp,
soluble carbohydrate n proteins

complex carbo degrade

resistant material(lignin) degrade

zones

shallow

coal, kerogen and oil and gas

methanogenic

deep hot

majority are Firmicute species

deep

chemolithoautotrophs survive
only on H2, CO2, H2O

differ from in photic zome of open ocean

differ because plant or insect released degradative enzyme
do not rapidly diffuse away