Rubin-Blum et al. (2017) describedCycloclasticus as a symbiont with mussels and
sponges dwelling in deep-sea gas and oil seeps (Rubin-Blum et al. 2017) and
oil-aggregates to diatoms in Arctic region (Netzer et al. 2018). The halophilic strain
Thalassospira sp. SL5–1 (Zhou et al. 2016) is able to degrade pyrene through both
o-phthalic acid and gentisic acid. Particularly, identification of phthalic acid and
salicylic acid showed that phthalate and salicylic acid routes were simultaneously
contained in the pyrene degradation, which was remarkably different from those for
other pyrene-degraders. The polycyclic aromatic hydrocarbons metabolic pathway
occurring in mixed microbial consortia is expected to be a more complex combination than those described in pure cultures considering that the metabolic intermediates can be used and transferred among different microorganisms (Zhou et al. 2016).
Cycloclasticus genus includes strains specialized in the degradation of polycyclic
aromatic hydrocarbons. Strains belonging to this genus harbor three large operons
encoding for a set of four different classes of dioxygenases (Messina et al. 2016).
The role of Alphaproteobacteria on the polycyclic aromatic hydrocarbons degradation is particularly interesting, due to their putative capability to conclude polycyclic
aromatic hydrocarbons degradation by using intermediate action, which both eliminates toxic compounds from the medium and maintains enzymatic action at the
same rate. A recent comparative genomic study of genera affiliated with
Alphaproteobacteria, for example, marine Roseobacter, Thalassospira, and
Erytrobacter clade, revealed the presence of numerous pathways for the catabolism
of structurally diverse aromatic substrates.
7.3 Biodegradation of Hydrocarbons by Microalgae
and Cyanobacteria
7.3.1 Microalgae Oil Degradation
Microalgae and cyanobacteria have, firstly, a pivotal role in the primary production,
but due to their capability in the carbon fixation and nutrients recycling, their
involvement on hydrocarbonsbiodegradation processes was hypothesized (Ghosal
et al. 2016; Srivastava and Kumar 2019). Many marine phototrophic microorganisms exhibit the capability to survive in marine areas seriously affected by oil
pollution, especially those species adapted to coastal areas where oil inputs can
frequently occur (Abed et al. 2006). Some cyanobacteria and diatoms are particularly abundant even in oil-contaminated sediments (Coulon et al. 2012). The capability of chlorophytes and diatoms but also cyanobacteria, to degrade hydrocarbons,
especially aromatic fractions, is rarely reported (Table 7.2 and Table 7.3), often with
conflicting results. Accordingly, it is still an open question whether microalgae and
cyanobacteria would cooperate with specialist aerobic hydrocarbonoclastic bacteria
to break down hydrocarbons or they are involved only in the partial oxidation
(Cerniglia et al. 1980b). As an example, first experiments were performed on
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R. Denaro et al.
sponges dwelling in deep-sea gas and oil seeps (Rubin-Blum et al. 2017) and
oil-aggregates to diatoms in Arctic region (Netzer et al. 2018). The halophilic strain
Thalassospira sp. SL5–1 (Zhou et al. 2016) is able to degrade pyrene through both
o-phthalic acid and gentisic acid. Particularly, identification of phthalic acid and
salicylic acid showed that phthalate and salicylic acid routes were simultaneously
contained in the pyrene degradation, which was remarkably different from those for
other pyrene-degraders. The polycyclic aromatic hydrocarbons metabolic pathway
occurring in mixed microbial consortia is expected to be a more complex combination than those described in pure cultures considering that the metabolic intermediates can be used and transferred among different microorganisms (Zhou et al. 2016).
Cycloclasticus genus includes strains specialized in the degradation of polycyclic
aromatic hydrocarbons. Strains belonging to this genus harbor three large operons
encoding for a set of four different classes of dioxygenases (Messina et al. 2016).
The role of Alphaproteobacteria on the polycyclic aromatic hydrocarbons degradation is particularly interesting, due to their putative capability to conclude polycyclic
aromatic hydrocarbons degradation by using intermediate action, which both eliminates toxic compounds from the medium and maintains enzymatic action at the
same rate. A recent comparative genomic study of genera affiliated with
Alphaproteobacteria, for example, marine Roseobacter, Thalassospira, and
Erytrobacter clade, revealed the presence of numerous pathways for the catabolism
of structurally diverse aromatic substrates.
7.3 Biodegradation of Hydrocarbons by Microalgae
and Cyanobacteria
7.3.1 Microalgae Oil Degradation
Microalgae and cyanobacteria have, firstly, a pivotal role in the primary production,
but due to their capability in the carbon fixation and nutrients recycling, their
involvement on hydrocarbonsbiodegradation processes was hypothesized (Ghosal
et al. 2016; Srivastava and Kumar 2019). Many marine phototrophic microorganisms exhibit the capability to survive in marine areas seriously affected by oil
pollution, especially those species adapted to coastal areas where oil inputs can
frequently occur (Abed et al. 2006). Some cyanobacteria and diatoms are particularly abundant even in oil-contaminated sediments (Coulon et al. 2012). The capability of chlorophytes and diatoms but also cyanobacteria, to degrade hydrocarbons,
especially aromatic fractions, is rarely reported (Table 7.2 and Table 7.3), often with
conflicting results. Accordingly, it is still an open question whether microalgae and
cyanobacteria would cooperate with specialist aerobic hydrocarbonoclastic bacteria
to break down hydrocarbons or they are involved only in the partial oxidation
(Cerniglia et al. 1980b). As an example, first experiments were performed on
204
R. Denaro et al.