Ecology Lec

• Microbial ecology of infections includes the biogeography of polymicrobial infection and using microbial ecology in therapeutic strategies
• Dimethylsulfide (DMS)


  Compound that creates the sulfur smell at the beach or sea
• Atmospheric Microbes


  • Air travels from long distances, microbes in the air can come from different sources, such as spores being dispersed by air

  
• Factors of forest air that can make us feel healthier

  • Beneficial bacteria
  • Plant-derived essential oils
  • Negatively-charged ion
• Bioaerosols


  Primary biological aerosol particles, solid airborne particles derived from organisms, including microorganisms and fragments of biological materials such as plant debris and animal dander
• Bioaerosols can range in size from virus to large pollen from trees, and include fungal spores and fungal hyphae
• Near-surface air


  • Contains fungal spores, hyphal fragments, and algae
• Bioaerosol cycling


  1. Emission from source

  2. Transport, transformation

  3. Stress, aging, viability

  4. Cloud processing

  5. Dry deposition

  6. Wet deposition
• Aeromicrobiological Pathway


  1. Launching

  2. Transport

  3. Deposition
• Launching


  The particle gets suspended in air via physical processes involving water, wind, turbulence, both natural and man-made, or via biological processes such as the release of spores by fungi or when a person sneezes
• Transport


  Particles in the air get transferred from one point to another through air currents, resulting in diffusion or scattering of the particles from high to low concentration gradient
• Deposition


  The particles in the air are deposited on a surface by gravitational setting, surface impaction, or rain deposition
• Upper boundary of the biosphere has been studied, with lower altitude having higher number of colonies
• Urban aerosols harbor diverse and dynamic bacterial populations

  
• Bacterial groups detected in urban air

  • Acidobacteria
  • Actinobacteria
  • Cyanobacteria
  • Bacteroidetes
  • Proteobacteria
  • Firmicutes

  
• Soil Prokaryote Diversity vs Prokaryotes in near surface air are almost the same
• Urban air in a tropical setting (Singapore) has comparable microbial diversity to ocean, soil, and human gut

  
• In air, majority is eukaryotes (fungi are dominant), while in soil and gut, majority is bacteria
• Higher species diversity in air is observed during daytime
• Ascomycota was found to be dominant in air, while Basidiomycota does not peak at noon time
• Atmosphere


  • Has a wide range of conditions that might support microbial growth, with density of microorganisms varying with space and time, and microbes can be metabolically active and stay long enough in the air to reproduce

  
• Latitudinal air cells


  Hadley cells (near equator), mid-latitude cells, and polar cells, which are suggested as possible biogeographic regions for microorganisms

  
• Atmospheric conditions


  • pH 3 to 7, near surface average temperature 15C, UV increasing with altitude, organic material <1 mg/liter, residence time 2.2 to 188.1 days for bacterial sizes

  
• Atmospheric conditions can support microbial growth, although fast growth rates are not expected due to limited nutrients

  
• ITCZ (Intertropical Convergence Zone)


  • Warm air goes up, loses its warmth, becomes cold air then is reflected to south and north regions, forming the Hadley cells
• Difference in temperature, pressure, and ozone holes in polar regions can affect the microbial profile in different atmospheric cells

  
• Dust, microbes, and pollen can travel across oceans in 3 to 9 days, driven by air circulations and wind patterns
• Health risks from inhaled dust

  • Penetration of particulates <10 micrometers in size into the lungs, heavy metal content, pollens and allergens, pathogens such as COVID-19
• Applications of air quality testing

  • Indoor: Hospital, Pharmaceutical industry, Food manufacturing

  Outdoor: Particulates and bioaerosols including pollen
• Near surface air study

  Air sampler SASS 3100 sucks air, particulates and biological aerosols are collected on a filter, DNA extraction, nucleic acid analysis
• Passive air monitoring


  Using settling plates or fallout plates, where open agar plates are exposed to the environment and particles passively fall out or settle on the surface
• Active air monitoring


  Particulate or viable air samplers actively draw a large volume of air into a chamber and collect viable microorganisms or detect the number and minimal size of particles
• Active air monitoring provides immediate results for real-time monitoring and control, while active viable air sampling does not provide real-time results as the growth medium needs to be incubated
• Active air monitoring methods

  Particulate or viable air samplers
• Particulate air sample


  • Detects the number and minimal size of particles but does not differentiate between viable and non-viable particles
  • Provides immediate results for real-time monitoring and control
• Viable air sampler


  • Collects viable microorganisms from the air that is sampled
  • Large volume of air is actively drawn into a chamber and forced along the surface of a growth medium collecting viable microorganisms from the air being sampled
  • Does not provide for real-time monitoring and control since the growth medium needs to be incubated before viability counting
• Air monitoring


  1. Air is actively drawn through a sample horn

  2. Particles found present in the environment will scatter the laser light according to its size

  3. The monitor can detect particles in sizes ranging from 0.3um to 5um

  4. The counter generates a readout that reveals the size and number of particles in the environment

  5. Air is pulled through the many holes of the cover plate and gets directed along the surface of an agar plate

  6. Viable particulates get evenly deposited across the growth medium

  7. The growth surface is incubated for 7–14 days and evaluated for contamination level
• Membrane filtration


  1. Air or another gas is forced through a filter on which microbes can adhere

  2. The filter membrane is then placed on a growth medium, incubated, and evaluated for contamination levels
• Monitor floors, walls, product–contact surfaces, and equipment used for the manufacturing of pharma drug products should also be tested on a regular basis
• Test using


  Touch plates, swabs, and contact plates