Gammaproteobacteria dominate initially the community
and then Alphaproteobacteria and Bacillaceae take over.
These developments confirm that the bacterial communities
adapt to the presence of the pollutant, and then the microbial
mat regains its original structure 1 year after infection.
Functional studies have been undertaken to highlight the
mechanisms of adaptation to the presence of oil.
Mats of the Etang de Berre exposed to chronic contamination were characterized by molecular and cultural
approaches. Analyses by DGGE and RISA showed that
the two sites exposed to different levels of contamination
possessed different bacterial communities but similar
diversity indices (Villanueva et al. 2007). Comparing the
community composition showed that Gamma- and
Alphaproteobacteria were abundant in both sites, while
phylotypes associated with Deltaproteobacteria and
group WS3 were detected in the most polluted site. Consortia capable of degrading hydrocarbons were obtained
from enrichment media. The identification of bacterial species present in these consortia showed that the species
involved in oil degradation belonged to the order
Rhodobacterales. These observations suggest that pollution does not affect the richness of microbial mats, and it
seems that the populations involved in the degradation
represent only a minor fraction of the bacterial community.
8.5.3 Aquatic Biodiversity, Water Blooms
Issues that arise with respect to aquatic pathogens involve
animals and man, pollution, currents, and especially algal
blooms. Rivers carry bacterial communities that vary in size
and composition depending on inocula from sewage treatment plants, fecal contamination (septic tanks, breeding
animals), runoff from surfaces, etc. Bacterial communities
also fluctuate depending on irradiation, temperature,
nutrients, and predation by phage or eukaryotic (Jardillier
et al. 2005). These fluctuations are especially studied to
identify the arrival of fecal coliforms associated to agricultural and water treatment plants (Lemarchand and Lebaron
2003). A body of work based on a comparison of molecular
and cultural approaches reveals that the physiological state
of bacteria in the community plays a central role in the
transmission of diseases to humans because of the presence
of viable but non-culturable strains (cf. Box 15.4), it thus
seems important to use more than one type of approach.
The other major problem with bacterial diversity in aquatic
biotopes is understanding the factors controlling algal blooms.
These sudden increases in the proportion of cyanobacteria are
not only spectacular and threatening to fish, there is also a
public health risk due to the presence of toxin-producing
species that are taken up the food chain and in particular in
Biomass of
H. excentricum
Biomass of
M. chthnoplastes
Vector scaling: 5.26
pH
O 2
AXIS 2 (11.632 %)
AXIS 1 (17.208 %)
15H
4H
0.3-0.4 mm
2.6-2.8 mm
1.2-1.3 mm
0-0.1 mm
0.3-0.4 mm
0.6-0.7 mm
0.9-1 mm
2-2.2 mm
1.8-1.9 mm
1.5-1.6 mm
0.6-0.7 mm
0-0.1 mm
2-2.2 mm
1.2-1.3 mm
1.5-1.6 mm
0.9-1 mm
1.8-1.9 mm
Stot
H 2 S
3.5
2.8
2.1
1.4
-0.7
-1.4
-2.1
-2.8
-3.5
-3.5
-2.8
-2.1
0.7
1.4
2.1
2.8
3.5
Fig. 8.5 Canonical
correspondence analysis (CCA):
comparing anoxygenic
communities of phototrophic
bacteria (APB) for each microbial
mats depth during the daytime at
15 h (closed triangles) to those
during the night at 4 h (open
triangles), and the following
environmental parameters:
Microcoleus chthonoplastes
biomass, pH, and concentration of
O 2 , H 2 S, and Stot (total sulfur)
(Courtesy of Robert Duran)
8 Biodiversity and Microbial Ecosystems Functioning
281
and then Alphaproteobacteria and Bacillaceae take over.
These developments confirm that the bacterial communities
adapt to the presence of the pollutant, and then the microbial
mat regains its original structure 1 year after infection.
Functional studies have been undertaken to highlight the
mechanisms of adaptation to the presence of oil.
Mats of the Etang de Berre exposed to chronic contamination were characterized by molecular and cultural
approaches. Analyses by DGGE and RISA showed that
the two sites exposed to different levels of contamination
possessed different bacterial communities but similar
diversity indices (Villanueva et al. 2007). Comparing the
community composition showed that Gamma- and
Alphaproteobacteria were abundant in both sites, while
phylotypes associated with Deltaproteobacteria and
group WS3 were detected in the most polluted site. Consortia capable of degrading hydrocarbons were obtained
from enrichment media. The identification of bacterial species present in these consortia showed that the species
involved in oil degradation belonged to the order
Rhodobacterales. These observations suggest that pollution does not affect the richness of microbial mats, and it
seems that the populations involved in the degradation
represent only a minor fraction of the bacterial community.
8.5.3 Aquatic Biodiversity, Water Blooms
Issues that arise with respect to aquatic pathogens involve
animals and man, pollution, currents, and especially algal
blooms. Rivers carry bacterial communities that vary in size
and composition depending on inocula from sewage treatment plants, fecal contamination (septic tanks, breeding
animals), runoff from surfaces, etc. Bacterial communities
also fluctuate depending on irradiation, temperature,
nutrients, and predation by phage or eukaryotic (Jardillier
et al. 2005). These fluctuations are especially studied to
identify the arrival of fecal coliforms associated to agricultural and water treatment plants (Lemarchand and Lebaron
2003). A body of work based on a comparison of molecular
and cultural approaches reveals that the physiological state
of bacteria in the community plays a central role in the
transmission of diseases to humans because of the presence
of viable but non-culturable strains (cf. Box 15.4), it thus
seems important to use more than one type of approach.
The other major problem with bacterial diversity in aquatic
biotopes is understanding the factors controlling algal blooms.
These sudden increases in the proportion of cyanobacteria are
not only spectacular and threatening to fish, there is also a
public health risk due to the presence of toxin-producing
species that are taken up the food chain and in particular in
Biomass of
H. excentricum
Biomass of
M. chthnoplastes
Vector scaling: 5.26
pH
O 2
AXIS 2 (11.632 %)
AXIS 1 (17.208 %)
15H
4H
0.3-0.4 mm
2.6-2.8 mm
1.2-1.3 mm
0-0.1 mm
0.3-0.4 mm
0.6-0.7 mm
0.9-1 mm
2-2.2 mm
1.8-1.9 mm
1.5-1.6 mm
0.6-0.7 mm
0-0.1 mm
2-2.2 mm
1.2-1.3 mm
1.5-1.6 mm
0.9-1 mm
1.8-1.9 mm
Stot
H 2 S
3.5
2.8
2.1
1.4
-0.7
-1.4
-2.1
-2.8
-3.5
-3.5
-2.8
-2.1
0.7
1.4
2.1
2.8
3.5
Fig. 8.5 Canonical
correspondence analysis (CCA):
comparing anoxygenic
communities of phototrophic
bacteria (APB) for each microbial
mats depth during the daytime at
15 h (closed triangles) to those
during the night at 4 h (open
triangles), and the following
environmental parameters:
Microcoleus chthonoplastes
biomass, pH, and concentration of
O 2 , H 2 S, and Stot (total sulfur)
(Courtesy of Robert Duran)
8 Biodiversity and Microbial Ecosystems Functioning
281