Microbes & Nutrient Cycling

microbiology

study of microscopic organisms such as bacteria, viruses, fungi, protozoa, and algae

Microbiome

collective genomes of all microbes in an environment

microbiota

community of microorganisms themselves

Human body contains roughly as many bacterial cells as

human cells

Herbivores microbial C/N ratio

higher due to plant-based diets (more carbon) and longer intestine

Carnivore microbial C/N ratio

lower with faster turnover and protein-rich diets

What does the microbiome digest?

nutrients not digested or absorbed by teh host

Postbiotics

non-living microbial byproducts that provide a beneficial effect on the host

True/False. There is no gut microbiota variation across animals.

False

Macronutrients

elements required in large amounts for growth and development (P, K, C, H, O, Mg, N)

Micronutrients

elements required in trace amounts for vital biochemical functions (Fe, Cu, Ni, Zn, Mn, Cl)

Limiting Nutrient

nutrients that limit the growth, abundance, or distribution of a population of organisms in an ecosystem due to their scarcity

Common limiting Nutrients in soil and aquatic systems 

phosphorous, nitrogen, iron

Law of the Minimum

productivity dictated not by total resources available, but by the scarcest resource (limiting factor)

Can N₂ be used for growth by living organisms?

no

Nitrogen Cycle

abundance N₂ is fixed by microorganisms to form nitrogen compounds that are used by other organisms to sustain life

Ammonification

process converting organic nitrogen (amino acids, proteins, and nucleic acids in dead plants, animals, or microbes) into inorganic nitrogen like ammonia (NH₃) or ammonium (NH₄⁺)

pH < 7.5, NH₃ is

converted rapidly to NH₄⁺

Decomposers

earthworms, termites, slugs, snails, bacteria, and fungi use enzymes to degrade plant material

What do microorganisms use to degrade N₂-containing molecules?

enzymes

Nitrogen Fixation

the process by which atmospheric inorganic nitrogen gas (N₂), which most organisms cannot use, is converted into biologically available inorganic forms, such as ammonia (NH₃) or ammonium (NH₄⁺); energy intensive process; performed by selected bacteria and actinomycetes; performed in nitrogen fixing crops

What environments is nitrogen fixation beneficial?

areas of low nitrogen; hot, aquatic, acidic, inorganic nitrogen

Nitrification

converts ammonium (NH₄⁺), which can be toxic to plants at high concentrations, into nitrate (NO₃^-), the form most plants prefer for uptake; regulates nitrogen availability and soil fertility

Nitrification process

ammonia → nitrite (NO₂^-) by nitrosomonas and nitrite → nitrate (NO₃^-) by nitrobacter

Spatial Subsidy

a resource (nutrients, prey, detritus) gets transported from one habitat to another, increasing the productivity of the organisms living there; ex: salmon migration