EXAM 2

• Abiotic stresses

  1. light

  • sunlight does not penetrate beyond the top few centimeters of the soil surface
  • phototropic microorganisms are therefore limited to the top few centimeters of soil
  • e.g. algae, lichen
• Biotic stresses are caused by living organisms such as pathogens, insects, weeds, animals, birds, rodents, nematodes, fungi, bacteria, viruses, protozoa, parasites, etc.
• algae 


  grows on stagnant water
• 2. soil moisture

  • availability of water is critical for microbial activity
  • optimal microbial activity occurs at -0.1 atm, which is the transition between capillary water and free water
  • fungi are most desiccation resistant, followed by actinomycetes and finally the bacteria
• 3. soil temperature

  • psychrophilic (prefer <20C)
  • mesophilic (prefer 20C - 45C)
  • thermophilic (45C-90C)
  • hyperthermophilic (>90C)
  • most soil organisms are mesophilic because of the buffering effect of soil on soil temperature, particularly at depths beneath the soil surface
• 4. soil pH

  • undisturbed soils usually have soil pH values within the range of 6-8, and most soil organisms have pH optima within this range
  • acidithiobacillus thiooxidans, an organism that oxidizes to sulfur to sulfuric acid has a pH optimum of 2-3
• autotrophic microorganism 


  gumagawa ng sariling environment/nutrients to proliferate
• 5. soil texture

  • all soils contain microbial communities regardless of the soil texture
  • soils with mixture of sand, silt, and clay particles offer a more favorable habitat for organisms because they hold more nutrients, water, and air flow than do pure sands or clays
• 6. soil nutrients

  • carbon and nitrogen are generally the most important limiting nutrients that are found in soils
  • major exception to this is the plant
• 7. redox potential

  • measurement of the tendency of an environment to oxidize or reduce substrates
  • aerobic soil - oxidizing environment - Eh = 800 mV
• microorganisms in surface soils

  1. bacteria
• 2. actinomycetes

  • source of natural product and antibiotics e.g. steptomycin
  • produce geosmin, the compound which gives soil and water a characteristic earthy odor
  • capable of degradation of complex organic molecules
  • capable of biological nitrogen fixation with species of the non-legume-associated frankia
• 3. archaea

  • acrhaea contribute to multiple soil processes including the biogeochemical cycling of C, N and S
  • ammonia oxidizing archaeans (AOA) in general, AOA appear to be more important to ammonia oxidation in environments that have lower levels of N such as natural ecosystems
• 4. Fungi

  • despite their lower numbers compared with bacteria, fungi usually contribute to a higher proportion of the total soil microbial biomass
• beneficial fungi

  • penicillium and aspergillus - involved in nutrient recycling; important in the development of the soil structure because they physically entrap soil particles with fungal hyphae
  • phanerochaete chrysosporium - can also degrade a variety of pollutant molecules
• 5. algae

  • are typically phototropic and thus would be expected to survive and metabolize in the presence of light and CO2
  • algal metabolism is critical soil formation in two ways:
• detrimental algae

  1. chlamydomonas- most common algae found in acidic soils
  2. diatoms - found primarily in neutral and alkaline soil
  3. in temperate soils, the relative abundance of the major algal group follows the order of green algae>diatoms> red algae
• protozoa

  • there are three major categories of protozoa: the flagellates, the amoebae and the ciliates
  • there is an evidence that they may also be involved to some extent, int the decomposition of soil organic matter
  • protozoan population of a soil is often correlated with the bacterial population which is the major food source present
• II. aeromicrobiology

  • atmosphere is an inhospitable climate for microorganisms mainly because of desiccation stress
  • limited time frame in which microbes can remain biologically active
  • spore-forming bacteria, molds, fungi, and cyst-forming protozoa have specific mechanisms that protect them from harsh environment
• 1. relative humidity

  • relative water content of the air
  • in general, most G- bacteria associated with aerosols tend to survive for longer periods at low to mid relative levels of humidities, with enhanced decay at the relative humidities above 80%
  • opposite tends to be true for gram-positive bacteria, which tend to remain viable longer in association with high relative humidities
• 2. temperature

  • high temperatures promote inactivation, mainly associated with desiccation and protein denature, and lower temperatures promote longer survival times
  • when temperatures approach freezing, however, some microorganism lose viability because of the formation of ice crystals on their surface
• radiation

  • dienococcuss radiodurans - soil bacterium that is considered the most highly radiation-resistant organism, has the ability to enzymatically repair damage to chromosomal DNA
• 4. oxygen, open air factors (oafs) and ions

  • oxygen toxicity is important in the inactivation of microorganisms when O2 is converted to more reactive forms (Superoxide radicals, hydrogen peroxide, and hydroxide radicals)
  • OAF is term coined to describe an environmental effect that cannot be replicated in laboratory experimental setthings
• aerosolization of indigenous soil pathogens

  • spores can potentially be aerosolized and cause human infections
  • important fungal geo-indigenous pathoens include coccidioides immitis and histoplasma capsulatum
  • bacillus anthracis is a bacterial geo-indigenous pathogen that causes lethal disease in humans via pulmonary, gastrointestinal or cutaneous modes of infections
• microbiology in the clouds

  • some microorganisms, called ice nucelators, efficiently catalyze ice formation and may play a role in the formation and precipitation in the clouds
• agriculture

  • contamination of crops and animals via bioaerosols has a large worldwide economic impact
  • rice and wheat are two of the major staple crops that are paramount to world food security
• agriculture

  • airborne spread of pathogenic microorganisms is also highly important in the animal husbandry industry
  • occurence of foot-and-mouth disease is an example of bioaerosols
• important airborne toxins

  • clostridium botulinum (botulinum A toxin) - potential biological warfare agent; lethal dose for botulinum toxin by inhalation is 0.3 microg, with death occurring 12 hours after exposure
• Environmental microbiology

  • study of microbes within all habitats and their detrimental and beneficial impacts on health and welfare
• water treatment

  • water
  • waterborne disease reduction
  • norovirus and legionella
• food consumption

  • food
  • foodborne disease
  • clostridium botulinum, E. coli O157:H7
• indoor activities

  • fomites
  • respiratory disease
  • rhinovirus
• breathing

  • air
  • legionellosis
  • legionella pneumophila
• enhanced microbial antibiotic resistance

  • hospitals
  • antibiotic-resistant microbial infections
  • methicillin-resistant staphylococcus aureus
• nutrient cycling

  • soil
  • maintenance of biogeochemical cycling
  • soil heterotrophic bacteria
• rhizosphere/plant interactions

  • soil
  • enhanced plant growth
  • rhizobia mycorrhizal fungi
• bioremediation

  • soil
  • degradation of toxic organics
  • pseudomonas spp.
• freshwater type

  • microorganisms thrive more here than in the deep sea due to high salinity content in the sea, very rich soil and as well as other microorganisms used as nutrients
• emerging environmentally transmitted microbial pathogens and biological agents

  
  

  1. studied to reduce their detrimental effects on people
  2. physical and chemical components/characteristics are also studied to know how to eradicate them
• adenovirus

  • virus
  • water, air, fomites
  • most resistant waterborne agent to UV light
  • respiratory, gastroenteritis, eye, ear infections