(Rhodococcus rhodochrous, Arthrobacter nicotianae, Pseudomonas sp., and Bacillus sp.), associated with cyanobacterial cultures of Microcoleus c. and Phormidium
c., able to oxidize n-alkanes although cyanobacteria directly contributed to hydrocarbon uptake and oxidation.
Recently, Severin and Erdner (2019) have explained the presence of
hydrocarbon-degrading taxa in the microbiome of dinoflagellates with their high
content of triacylglycerols, a precursor of biodiesel (Harrington et al. 1970;
Vasudevan and Briggs 2008; Fuentes-Grünewald et al. 2009). Hydrocarbondegrading bacteria are listed among the few examples of microorganisms that
produce triacylglycerols as reserve compounds, which could be used as a feedstock
by dinoflagellates. Moreover, they have evidenced a correlation with the capability
of consortium to resist and degrade oil.
According to the evidence reported above, the natural occurring
hydrocarbonsbiodegradation processes can be certainly inferred in the light of
synergic actions of a consortium, more than a monotype organism. Moreover, it
seems that the mechanism of positive interaction is species-specific as the
phycosphere different algae (Ramanan et al. 2016; Fuentes-Grünewald et al.
2016). Indeed, the algae–bacteria association can have a negative influence. For
example, in limiting-nutrients conditions, competition for the use of bioavailable
nutrients can occur. Furthermore, the pH of the medium can vary causing
alkalization and acidification of the phycosphere. For instance, the metabolic activity
during the flowering of cyanobacteria induces an increase of pH, while the production of poly-g-glutamic acid by bacteria significantly reduces aquatic pH and inhibits
the growth of microalgae. Moreover, substances produced both by algae and
bacteria can interfere with bacterial quorum sensing and inhibit cyanobacteria
photosynthesis.
In order to produce the desired effects (e.g., bioremediation) from the concerted
action of algae and bacteria, it is necessary to investigate the regulation of interactions at the molecular level. The biotechnological application of this knowledge is
already applied not only in the field of bioremediation but also in the sectors of
wastewater treatment and sustainable aquaculture.
7.5 Conclusions
– Algae–bacteria consortia have been described as efficient systems for hydrocarbons degradation, even for tough substrates as aromatic ones.
– Few studies report in situ investigation and are mostly carried out in artificial
systems.
– The mechanisms of interaction during bioremediation processes are still unclear.
Axenic cultures of microalgae do not seem able to degrade hydrocarbons while
the degradation of hydrocarbons is observed if a microbiome (hydrocarbonsdegraders) is associated with the same species There is no evidence of the
presence of the classical genetic signatures specific for hydrocarbons degradation
7 Biodegradation of Hydrocarbons in Marine Environment
213
c., able to oxidize n-alkanes although cyanobacteria directly contributed to hydrocarbon uptake and oxidation.
Recently, Severin and Erdner (2019) have explained the presence of
hydrocarbon-degrading taxa in the microbiome of dinoflagellates with their high
content of triacylglycerols, a precursor of biodiesel (Harrington et al. 1970;
Vasudevan and Briggs 2008; Fuentes-Grünewald et al. 2009). Hydrocarbondegrading bacteria are listed among the few examples of microorganisms that
produce triacylglycerols as reserve compounds, which could be used as a feedstock
by dinoflagellates. Moreover, they have evidenced a correlation with the capability
of consortium to resist and degrade oil.
According to the evidence reported above, the natural occurring
hydrocarbonsbiodegradation processes can be certainly inferred in the light of
synergic actions of a consortium, more than a monotype organism. Moreover, it
seems that the mechanism of positive interaction is species-specific as the
phycosphere different algae (Ramanan et al. 2016; Fuentes-Grünewald et al.
2016). Indeed, the algae–bacteria association can have a negative influence. For
example, in limiting-nutrients conditions, competition for the use of bioavailable
nutrients can occur. Furthermore, the pH of the medium can vary causing
alkalization and acidification of the phycosphere. For instance, the metabolic activity
during the flowering of cyanobacteria induces an increase of pH, while the production of poly-g-glutamic acid by bacteria significantly reduces aquatic pH and inhibits
the growth of microalgae. Moreover, substances produced both by algae and
bacteria can interfere with bacterial quorum sensing and inhibit cyanobacteria
photosynthesis.
In order to produce the desired effects (e.g., bioremediation) from the concerted
action of algae and bacteria, it is necessary to investigate the regulation of interactions at the molecular level. The biotechnological application of this knowledge is
already applied not only in the field of bioremediation but also in the sectors of
wastewater treatment and sustainable aquaculture.
7.5 Conclusions
– Algae–bacteria consortia have been described as efficient systems for hydrocarbons degradation, even for tough substrates as aromatic ones.
– Few studies report in situ investigation and are mostly carried out in artificial
systems.
– The mechanisms of interaction during bioremediation processes are still unclear.
Axenic cultures of microalgae do not seem able to degrade hydrocarbons while
the degradation of hydrocarbons is observed if a microbiome (hydrocarbonsdegraders) is associated with the same species There is no evidence of the
presence of the classical genetic signatures specific for hydrocarbons degradation
7 Biodegradation of Hydrocarbons in Marine Environment
213