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LITHOSPHERE 4713697_orig (MICROBE'S BEHAVIOUR IN DIFFERENT SOIL…
LITHOSPHERE
MICROBIAL SIZE
Bacteria - large number, smaller size, smaller biomass
iron-oxidizing bacteria
found on the surface of volcanic rocks
most are heterotrophs
Actinobacteria
iron within the rocks as source of energy
oxidized iron gives the bacteria their rusty color
diameter of approximately 0.001 mm
Actinomycetes - 10 times smaller in number, larger in size, same biomass with bacteria
Fungus - small in number, larger in size
filaments are bigger, 0.005 mm
Healthy soil
contains up to 3,000 million bacteria
500,000 fungi plus actinomycetes, algae and protozoa
MICROBIAL CELL STRUCTURE
most fungi live in soil need oxygen in their growth
protozoan used their flagella to propel or pull their way through soil
ciliates protozoan use the fine cilia along their bodies like oarsto move rapidly through soil
coliform bacteria travel from 0.6m in fine sandy loam to 830m is sand-gravel
bacteriophage T4 travelled up to 1.6km in a carbonate rock terrain area
MICROBIAL CELL REPLICATION
metabolic activity has been detected in soil at temperature as low as -39 degree celcius
fruiting body of fungi is often seen growing on fallen dead tree branches
Toadstools and mushrooms are the fruiting body of a large network of fungi hyphae in the soil
CELL NUTRITION
: :champagne:
autotroph : synthesize their own food from simple organic substance
heterotroph (mostly) : unable to synthesize their own food.
some are able to fix nitrogen eg:
nitrosomonas sp. and azobacter
organic and inorganic nutrients are distributed between the soil solution and the surface of mineral particles
Bacteria prefer to eat smaller soluble compounds, especially sugars and starch
Fungi feed on hard to decompose plant fibres and woody material including cellulose, lignin and plant fibres
Many minerals are needed in small amounts
Nitrogen, Phosphorus, Potassium, Sulphur, Sodium, Calcium, Magnesium, Manganese, Iron, Zinc, Copper, Molybdenum and Cobalt
An adequate supply of Nitrogen is needed for the rapid decomposition of organic matter
Optimum Phosphorus content for decomposition is 100:1
The optimum Carbon/Nitrogen ratio is 30:1
MICROBE'S BEHAVIOUR IN DIFFERENT TYPES AND PARTS OF ROCKS
At the surface of the rocks
exist as biofilms
moist and wet environment
breaks down/dissolves rock minerals by altering the soil's composition
symbiotic relationship between fungi and algae to form lichen
the minerals thus released from rock are consumed by the algae
holes and gaps continue to develop on the rock, exposing the rock further to physical and chemical weathering
chemical weathering = alters a rock's chemical composition (exchange of ions and cations)
physical weathering = breaks down a rock's physical structure (friction and impact)
depending on the chemicals involved, the rock might disintegrate entirely, or might simply become softer and more vulnerable to other forms of weathering
shatter rocks, rub away rock surfaces, or form cracks within the rock
through corrosive action by metabolic products such as ammonia, nitric acid, carbon dioxide, oxalic acid, citric acid and gluconic acid
holes and gaps continue to develop on the rock, exposing the rock further to physical and chemical weathering
physical weathering = breaks down a rock's physical structure by friction and impact
chemical weathering = alters a rock's chemical composition by exchange of ions and cations
shatter rocks, rub away rock surfaces, or form cracks within the rock
the rock might disintegrate entirely, or might simply become softer and more vulnerable to other forms of weathering due to the increase in exposed surface area
during weathering, minerals that were once bound in the rock structure are released
fungi release chemicals that break down rock minerals
chemicals released by microbes
soil is the product of rock weathering
organic acids released by microbes promotes weathering of primary minerals such as feldspars and secondary minerals, such as clay
Limestone rock
form cavities (hollow area in rock)
by causing dissolution of calcium carbonate
MICROBE'S BEHAVIOUR IN DIFFERENT SOIL CONDITIONS
Bacteria
Some bacteria survive in dry conditions by forming spores
prefer to grow in the thin layer of moisture surrounding clay particles
Fungi
more tolerant of dry conditions
grow better in large soil pores and can survive in dry conditions
Waterlogged
soils
anaerobic, low in Oxygen, slow microbial activity,
accumulate organic matter and often form peats
Very dry soil
microbial activity slows down, low organic matter and many individual microbes die
Some species survive harsh conditions by forming spores
When suitable moist conditions return spores germinate into rapidly growing microbes
Aeration
Aerobic
need gaseous oxygen to grow
Fungi grow better in well aerated soils and surface of soils
Anaerobic
survive in poorly aerated soils
Bacteria can tolerate poor aeration and can grow deeper in soils
ph
bacteria : range from 5-9, optimum at 7
actinomycetes : range from 6.5-9.5,optimum at 8
fungi : range from 2-7, optimum at 5
blue green bacteria : range from 6-9, optimum at >7
protozoan : range from 5-8, optimum at >7
Most soil microbes prefer a neutral pH level, sometimes fertilisers decrease soil pH and reduce microbe activity
Protozoa
need bacteria to eat and water in which to move
moisture plays a big role in determining which types of protozoa will be present and active
Temperature
growth rate of microorganisms increases with a rise in temperature
Tropical soils
higher temperatures
increased microbial activity
low organic matter
Alpine soils
soils experience annual freeze-thaw process
enriched with organic matter
textures are often dominated by a high coarse sand and fine gravel component
very cold climatic conditions
low microbial activity and contain high organic matter
extreme seasonal variations
winter
snowpack
bacterial communities were dominated by ubiquitous groups (i.e., beta-Proteobacteria)
snow-free seasons
other groups (i.e., Cyanobacteria) became more abundant
season had a strong effect on microbial community structures and soil properties
RELATED ARTICLES AND JOURNALS
Understanding Soil Microbes and Nutrient Cycle
Survivability of Microbes in Natural Environments and Their Ecological Impacts
Microbial Population Structures in Soil Particle Size Fractions of a Long-Term Fertilizer Field Experiment
how the microbes move in the soil environment ?