Air Environments Flashcards
Is air a good MO environment?
3 reasons why.
• not very good at all, nothing really lives in air, organisms in air are transitional
- dry, nutrient poor
- UV damage can be high
- conditions vary a lot - extremes
Microbial survival in aerosols depends on:
- type of MO
- relative humidity
- temperature
- radiation, O2, ions, pollutants
What are the variables to loss of biological activity is inactivity = Xt = X0e^-kt
Where: X = number of microbes k = inactivation constant
t = time
• k depends on the type of MO and environmental conditions
What bacteria and viruses are better at high and low humidity?
- Gram –’ve MOs survive better at low humidity
- Gram +’ve MOs survive better at high humidity
- enveloped viruses survive better at low humidity
- nonenveloped viruses survive better at high humidity • increasing temperature decreases survival
What does radiation damage? What is it?
- Damage due to alterations in nucleic acids (mainly DNA)
- Shorter UV and X-ray wavelengths are more damaging
How to protect against UV?
- protection is found in association with other particles, pigments, high RH, and cloud cover
- many orgs have repair mechanisms
- spores resistant
Survival of Bacillus spores in UV.
- Spores are dormant, but can return to active metabolism under opt conditions
- Spores can tolerate some UV damage. Spores that are damaged too much will not come out of dormancy
Bacillus spores anatomy
-Exposporium present in some Bacili, a loosely-fitting proteinaceuos structure
-Spore coat consists of >50 proteins. Function of each is unclear, but coat is important for resistance to chemicals, predation
-Core contains enzymes, DNA, ribosomes, tRNA and small molecules
6
Water content of the core ~27-55% (vs ~80% of vegetative cells)
What are Bacillus spores made of that helps with DNA UV damage?
- 5-15% of dry weight of Bacillus, Clostridium spores is dipicolinic acid
- Contributes to keeping the water content low (proteins, DNA that are not well hydrated appear to be more resistant to heat, UV)
- Chelates cations. Cations affect resistance to wet heat
Human diseases
Bacterial diseases Pulmonary tuberculosis Pneumonia Pulmonary anthrax Legionellosis Whooping cough Diphtheria
Fungal diseases
Aspergillosis Coccidioidomycosis
Viral diseases
Influenza Influenza virus Hantavirus pulmonary syndrome Hepatitis
Chicken pox
Common cold
Dengue fever
How many plant diseases are airborne?
70%
Whats the late blight of potato?
-Caused 1845 epidemic that spread from Belgium throughout Europe by mid- October
• started mid-June, ended mid October
• famine related deaths 750,000 to 1,000,000.
• population of Ireland went from 8,200,000 to 4,400,000 from 1840 to 1911.
Citrus disease
-Originated in SE Asia, spread almost world wide. In US since 1910s (arrived on seedlings). Waves of outbreaks. Eradicated in 1994. Isolated again in 1995. –Thought to be spread by hurricanes.
