Biotic and Abiotic Interactions

Vocabulary flashcards covering key abiotic and biotic concepts in microbial ecology, based on the lecture notes.

Abiotic filter

Non-living environmental factors (water, temperature, pH, salinity, pressure, light, oxygen) that shape microbial survival and distribution.

amensalism/antibiosis

A type of interaction where one organism is harmed while the other is unaffected, often through the production of toxic substances.

-•Negative effect on one partner, neutral on other.

•Example: antibiotic secretion in soil communities.

Biotic networks

Interactions among organisms (competition, predation, mutualism, etc.) that shape microbial communities.

Psychrophile

Microorganism that thrives at cold temperatures, typically below 15°C.

-osmolites protect against freezing → can cause crystals which burst and puncture cell; works by shifting freezing

Mesophile

Microorganism with optimal growth between approximately 15–40°C.

Thermophile

Microorganism with optimal growth between roughly 45–80°C.

Acidophile

Microorganism that grows best at acidic pH (pH < 5).

Neutrophile

Microorganism that grows best near neutral pH (pH ~6–8).

Alkaliphile

Microorganism that grows best at alkaline pH (pH > 8).

Halophile

Microorganism that requires NaCl (salt) for growth.

Extreme halophile

Halophile that dominates in highly saline environments with high salt tolerance.

Piezophile

Microorganism adapted to high hydrostatic pressure (deep-sea environments).

Piezotolerant

Microorganism that tolerates high pressure but does not require it.

Aerobe

Microorganism that uses oxygen for metabolism or tolerates oxygen.

Obligate aerobe

Microorganism that cannot grow without oxygen.

Facultative anaerobe

Microorganism that can grow with or without oxygen.

Obligate anaerobe

Microorganism that cannot tolerate oxygen and must live in its absence.

Microaerophile

Microorganism that requires low levels of oxygen for growth.

Aerotolerant

Microorganism that does not use oxygen but can tolerate its presence.

Water activity (aw)

Measure of available water for microbial growth; influenced by solutes.

Aqueous film

Thin layer of water around particles or in soils essential for microbial activity.

pH

•pH affects nutrient availability

•Acid rain: SOx, NOx → low pH freshwater.

•Ocean acidification: CO2 absorption → lower pH, impacts nitrification

• certain levels may be toxic to certain microbes

salt

•Halophiles need NaCl; extreme halophiles dominate saline lakes.

•Water activity (a_w) is key variable.

•Examples: salt ponds (red coloration).

pressure

•Deep ocean habitats: high pressure (>80 MPa).

•Piezophiles vs. piezotolerant microbes.

•Adaptations: membrane fluidity, protein stability.

• maintain cell structure

Euphotic zone

Upper, light-rich layer of an aquatic system where photosynthesis occurs.

Aphotic zone

Deeper layer with little to no light, where photosynthesis is limited.

Fundamental niche

Full range of environmental conditions under which a microbe can survive and reproduce.

Antagonism

Biotic interaction where one partner harms or inhibits another.

Competition

Interaction over limited resources; can be interference or exploitation.

Interference competition

Direct antagonistic actions (e.g., antibiotics, bacteriocins) to hinder rivals.

Exploitation competition

Indirect competition via faster uptake of limiting nutrients.

Mutualism

Biotic interaction where both partners benefit.

Commensalism

One partner benefits while the other is unaffected.

Parasitism

One partner benefits at the expense of the other.

Predation

Predator consumes prey; in microbes, includes protozoa and bacterial predators.

Syntrophy

Cross-feeding where one species uses byproducts of another (often in energy-rich partnerships like methanogenesis).

Horizontal gene transfer (HGT)

Transfer of genetic material between organisms other than parent to offspring; spreads traits like antibiotic resistance.

Endosymbiosis

One organism lives inside another; explains origins of mitochondria and chloroplasts.

Red Queen Hypothesis

Idea of ongoing evolutionary arms races in antagonistic interactions; organisms must continually adapt to remain in place.

OMZ (oxygen minimum zone)

Ocean or water column zone with very low dissolved oxygen, shaping microbial processes.

water

•All life requires water; microbes need aqueous films even in soils.

•Properties: polar, viscous, excellent solvent.

•Water availability determines growth vs. survival (spores, cysts).

hyperthermophiles

• can live above 80 degrees celcius

• mainly archaea