Environmental Microbiology of Aquatic and Waste Systems

4.1 Taxonomy of Microorganisms in Aquatic Environments 73

Biologicaly bound

Sulfur

SO 42 -

S^2 -

S^0

1

2

3

4 5

6

7

8

Assimilatory

section

Dissimilatory

section

Sulphuretum

(Organisms in the dissimilatory section

make up the sulphuretum)

Fig. 4.17 The biological sulfur cycle (After Luptakova 2007 ).
Key: 1 – Assimilatory sulfate reduction by plants, fungi and
bacteria; 2 – Death and decomposition by fungi and bacteria;
3 – Sulfide assimilation by bacteria and some plants; 4 – Excretion

of sulfate by animals; 5 – Dissimilatory sulfate­reducing

bacteria; 6 – Dissimilatory sulfur­reducing bacteria; 7 –

Phototrophic and chemotrophic sulfide-oxidizing bacteria; 8 –

Phototrophic and chemotrophic sulfur­oxidizing bacteria

Fig. 4.16 General
circulation of sulfur on
Earth (Modified from
Yamanaka 2008 )

H 2 S

S^0

H 2 SO 4

FeS 2

Pyrite

Sulfur-oxidizing bacteria

Photosynthetic bacteria

Volcanoes,

factories

Algae, Cyanobacteria

in oceans

(CH 3 ) 2 S

Dimethyl sulphide

Hot springs,

Volcanoes

Acidophilic iron-

oxidizing bacteria

Sulfate-reducing SO 2

bacteria

Animals Plants

Absorption

Excreta Death Death

Bacteria

H 2 O

O 2

Assimilatio&excretionn Bacteria

sulfur is not converted into organic compounds. The
rotten egg odor of hydrogen sulfide in the environment
usually indicates the presence of sulfate­reducing bac­
teria in nature. Sulfate­reducing bacteria are responsi­
ble for the rotten egg odors of salt marshes, mud flats,
and intestinal gas. They slowly degrade materials that
are rich in cellulose in anaerobic environments. Apart
from soil, sulfate reducing bacteria are found in various

habitats such as seas and oceans, mud and sediments

of freshwaters (rivers, lakes), waters rich in decaying

organic material, thermal or nonthermal sulfur springs,

mining waters from sulfide deposits, waters from

deposits of mineral oil and natural gas, industrial waste

waters from metallurgical industry, as well as in the

gastrointestinal tract of man and animals (Barton and

Hamilton 2007 ).