Chapter 15: Microbial Ecosystems

Ecosystems

Interactions and exchanges of materials between organisms and

their surrounding environment

Community of organisms

Primary producers, decomposers, and consumers

Primary producers

capture energy through photosynthesis.

Consumers

ingest/utilize stored photosynthetic energy.

Decomposers

recycle components back into environments.

Guilds

Members of communities can be grouped into functional groups

Niche

Specific functional role of an organism within an

ecosystem

quorum sensing

Groups/layers of microbes on a surface that interact with and

support each other

Biofilms

communities of microorganisms, such as bacteria, that adhere to surfaces and are embedded in a slimy, protective matrix

Formation often begins with appendaged bacteria forming the

primary layer on a surface.

exopolysaccharide (EPS).

EPS helps protect the biofilm but also helps form water-filled

channels for transport of nutrients and wastes.

microbial species grown in culture

Only 1-5% of the microbial species on Earth have been grown in culture !!

soil diversity

6-40,000

Direct sequencing

without growth or cloning

• Extraction of DNA from an environmental sample

Followed by PCR (often for rRNA genes) and sequencing then

compared to databases of known sequences for identification

Metagenomics

DNA from an environmental sample is used to construct a genomic

library.

• Genes from this “community” library can then be identified,

screened, and compared to other areas

Diversity

number of species

what percent of earths biomass is microbial?

Over 98%

oligotrophy

using nutrients at very

low concentrations.

dead zone formation

“Overfeeding” marine microbes can quickly lead to anoxic water

states

Dead zones

are areas without enough oxygen to support much

eukaryal life

Primary production

Carbon and energy are distributed through other levels by

zooplankton (consumers) feeding on phytoplankton and

through viral-mediated lysis.

Average seafloor depth

3,500 but deepest known has been 11,000

piezophiles

microbes that can withstand (and

sometimes require) these intense pressures to grow.

percent of primary production that reaches the seafloor

approximately 1 percent

Viruses in ocean

Probably 10 times more viruses exist in the oceans than

microbes

Stratified

Warmer aerobic upper

level

• Colder anoxygenic lower

level

• Thermocline layer in the

middle

o Stratification may be seasonal

or permanent.

o Layers dictate what can grow

and where

Biomes

Categories of ecosystems based on vegetation

characteristics

Soils are made up of..

humic (organics from

soil) material from incomplete breakdown of plant biomass.

rhizosphere

The area of soil immediately surrounding plant roots

possessing large amounts of organic carbon.

o Because of excess carbon, the area often has higher numbers

of microbes than bulk soi

DNA Sequence analysis

has allowed

for comparison of microbiota

from different soils.

• Soils that appear similar in

texture or composition can

vary dramatically in

microbial composition.

Bio-remediation

The use of microbes to consume and remove human-made

materials from soil.

o An example is the use of hydrocarbon degrading microbes in

petroleum-contaminated areas.

Deep subsurface microbiology

Microbes have been discovered in deep-sea vents, hot

springs, oil wells, and goldmine subterranean rock.

Hydrothermal vents

Volcanic activity releases minerals and gases into the

seawater.

• Microbes utilize these inorganics as primary energy and

electron sources to drive carbon fixation.

• Mats of microbes attract crustaceans, then larger

invertebrates and vertebrates.

• Microbes may even form symbiotic relationships with

these eukaryal organisms, further increasing biodiversity

in the communities

terrestrial hot springs

Milder temperatures, neutral pH, access to sunlight = Primary

production from cyanobacteria.

o Hotter acidic springs = Chemolithoautotrophs dominate as

conditions kill photosynthetic microbes.