Environmental microbiology

ENIRONMENTAL MICROBIOLOGY

I. Nutrient Cycling Processes

Microorganisms are an important part of every ecosystem
Biochemical cycling: oxidation and reduction of substances carried out by living organisms and/or abiotic processes that results in the cycling of elements within the ecosystem

A. Carbon Cycle

reduced form is methane
oxidized form is carbon monoxide and carbon dioxide
carbon fixation

B. Nitrogen Cycle

nitrification

denitrification

dissimilatory reduction of nitrogen

nitrogen assimilation

nitrogen fixation

assimilatory nitrate reduction

II. The Nature of Marine and Fresh Water Environments

A. Gradients

change in concentration of a substance over distance
Mixing of nutrients and waste products occur in freshwater and marine environments.
Winogradsky column

B. Surfaces and Biofilms

Biofilms are organized microbial systems consisting of layers of microbial cells in association with surfaces.

C. Microbial Mats

Large biofilms with macroscopic dimensions

D. Marine Environments

Water favors the growth of many microorganisms that are not found in soil.

great diversity of microorganisms found in aqueous environments

population of microorganisms affected by many factors

oligotrophic vs. eutrophic

phytoplankton

E. Freshwater Environments

Lakes often have temperature stratification
Epilimnion
Hypolimnion
Thermocline
Eutrophication: nutrient enrichment, stimulates growth of plants and microorganisms
Biochemical oxygen demand (BOD): amount of dissolved oxygen needed for microbial oxidation of biodegradable organic matter
Chemical oxygen demand (COD): amount of chemical oxidation required to convert organic matter in water to CO₂

F. Nutrient Removal from Water

1. Primary: removal of insoluble particulate materials

2. Secondary: biological removal of dissolved organic matter

e.g. trickling filters, extended aeration, activated sludge

3. Tertiary: Biological and chemical removal of inorganic nutrients

G. Water and Disease Transmission

1. Water purification

a) sedimentation basin

b) settling basin

c) filtration unit

d) disinfection

2. Microbiological analysis

a) introduction

must monitor water for presence of microorganisms
potable
use indicator organisms like coliforms

b) detection methods

1) membrane filters

2) presence-absence test

3) Colilert defined substrate test

ONPG and MUG

3. Water based diseases

a) introduction

many human pathogens spread by fecal oral route

b) toxic algal blooms

sudden growth of toxin-producing algae

1) red tide

dinoflagellates Gymnodinium and Gonyaulax

2) ciguatera poisoning

The toxin is produced by the dinoflagellate Gamierdiscus toxicus and is
concentrated in the flesh of fish.

c) Pfiesteria piscicida and Pfiesteria-like organisms

1) introduction

associated with numerous fish kills, primarily along Atlantic coast of the US

dinoflagellate

2) life cycle

at least 24 stages

3) pathogenesis

at least two different toxins

4) Symptoms in humans

include memory loss, confusion, acute skin burning, headache, skin rash, eye
irritation, muscle cramps, GI disturbances.

5) causes of outbreaks

excessive nutrients

6) summary

Pfiesteria fish kills can be difficult to detect.

Last updated July 3, 2007.