Ichor et al. 2016). Ellis (1997) reported that Anabaena cylindrica and Phormidium
foveolarum are able to metabolize hydrocarbons. Further studies conducted on
Agmenellum quadruplicatum and Oscillatoria sp. showed the transformation of
simple aromatic hydrocarbons as naphthalene to their metabolites under
photautotrophic conditions (Cerniglia et al. 1979; Cerniglia et al. 1980a, b, c).
Other studies showed that Oscillatoria sp. oxidizes biphenyl to 4-hydroxybiphenyl
and Agmenellum q. is able to oxidize phenanthrene (Narro et al. 1992). The oxidation of methylnaphthalene and biphenyl phenanthrene by cyanobacteria has been
also proved (Ibraheem 2010). Many authors have demonstrated that cyanobacteria
are able to metabolize aliphatic hydrocarbons. As an example, Microcoleus
chthonoplastes and Phormidium corium, isolated from marine oil-polluted environment, produced galactolipids and sulfolipids that included fatty acid derived from
the degradation of aliphatic hydrocarbons (Al-Hasan et al. 1998). The isolated
cyanobacteria Aphanothece conferta and Synechocystis aquatilis exhibited different
degradation efficiencies of aliphatic hydrocarbons, in relation to species and alkane
used (Ibraheem 2010). Other studies monitored degradation of petroleum hydrocarbons by the cyanobacteria Nostoc punctiforme and Spirulina platensis and showed
the total removal of decane, pentacosane, hexacosane, octacosane, and nonacosane
(Raghukumar et al. 2001; Radwan and Al-Hasan 2000; Cohen 2002). However,
many authors suggest that these findings were often ambiguous and, consequently,
the role of cyanobacteria on hydrocarbons degradation is not still clear (Radwan and
Al-Hasan 2000). As an example, the need of autotrophic microorganisms to use
carbon deriving from oil is also questioned by many authors (Sorkhoh et al. 1992;
Rippka 1988; Radwan and Al-Hasan 2000). It is noticeable that most of the studies
were conducted under non-axenic conditions, due to the difficult to obtain separated
bacterial and algal cultures (Abed and Koster 2005). On the other hand, several
authors have demonstrated the dominance of cyanobacteria in microbial communities occurring in many hydrocarbon-polluted sites (Sorkhoh et al. 1992;
Raghukumar et al. 2001; De Oteyza et al. 2004; Ibraheem 2010). Cyanobacteria
indeed frequently dominate microbial mats, laminated benthic microbial communities developing on the sediments of shallow protected water, such as estuaries,
lagoons, or sheltered beaches (Stal 2010; Stal et al. 2017). Oil-pollution in environment, both for natural seepage or caused by human activities can favor the development of microbial mats, where cyanobacteria are certainly associated to
hydrocarbon-degrading bacteria and fungi (Goñi-Urriza and Duran 2018). In particular, the surface layer of the mats, where the dominant members were cyanobacteria
and aerobic heterotrophic bacteria, shows a special capability in hydrocarbons
degradation (Abed et al. 2002; Cohen 2002; Abed and Koster 2005; Abed et al.
2006; Sanchez et al. 2005; Abed 2010; Goñi-Urriza and Duran 2018), probably due
to bacteria present in the microbial consortium (i.e., Marinobater and Alcanivoraxrelated members as well as species belonging to Rhodococcus, Sphingomonas,
Microbacterium genera) (Abed and Koster 2005). Microalgae and cyanobacteria
could participate to hydrocarbons degradation by performing biotransformation of
aromatic compounds into their hydroxylated intermediates that can be more easily
degraded by bacteria. Although they are not able to totally degrade pollutants, they
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R. Denaro et al.
foveolarum are able to metabolize hydrocarbons. Further studies conducted on
Agmenellum quadruplicatum and Oscillatoria sp. showed the transformation of
simple aromatic hydrocarbons as naphthalene to their metabolites under
photautotrophic conditions (Cerniglia et al. 1979; Cerniglia et al. 1980a, b, c).
Other studies showed that Oscillatoria sp. oxidizes biphenyl to 4-hydroxybiphenyl
and Agmenellum q. is able to oxidize phenanthrene (Narro et al. 1992). The oxidation of methylnaphthalene and biphenyl phenanthrene by cyanobacteria has been
also proved (Ibraheem 2010). Many authors have demonstrated that cyanobacteria
are able to metabolize aliphatic hydrocarbons. As an example, Microcoleus
chthonoplastes and Phormidium corium, isolated from marine oil-polluted environment, produced galactolipids and sulfolipids that included fatty acid derived from
the degradation of aliphatic hydrocarbons (Al-Hasan et al. 1998). The isolated
cyanobacteria Aphanothece conferta and Synechocystis aquatilis exhibited different
degradation efficiencies of aliphatic hydrocarbons, in relation to species and alkane
used (Ibraheem 2010). Other studies monitored degradation of petroleum hydrocarbons by the cyanobacteria Nostoc punctiforme and Spirulina platensis and showed
the total removal of decane, pentacosane, hexacosane, octacosane, and nonacosane
(Raghukumar et al. 2001; Radwan and Al-Hasan 2000; Cohen 2002). However,
many authors suggest that these findings were often ambiguous and, consequently,
the role of cyanobacteria on hydrocarbons degradation is not still clear (Radwan and
Al-Hasan 2000). As an example, the need of autotrophic microorganisms to use
carbon deriving from oil is also questioned by many authors (Sorkhoh et al. 1992;
Rippka 1988; Radwan and Al-Hasan 2000). It is noticeable that most of the studies
were conducted under non-axenic conditions, due to the difficult to obtain separated
bacterial and algal cultures (Abed and Koster 2005). On the other hand, several
authors have demonstrated the dominance of cyanobacteria in microbial communities occurring in many hydrocarbon-polluted sites (Sorkhoh et al. 1992;
Raghukumar et al. 2001; De Oteyza et al. 2004; Ibraheem 2010). Cyanobacteria
indeed frequently dominate microbial mats, laminated benthic microbial communities developing on the sediments of shallow protected water, such as estuaries,
lagoons, or sheltered beaches (Stal 2010; Stal et al. 2017). Oil-pollution in environment, both for natural seepage or caused by human activities can favor the development of microbial mats, where cyanobacteria are certainly associated to
hydrocarbon-degrading bacteria and fungi (Goñi-Urriza and Duran 2018). In particular, the surface layer of the mats, where the dominant members were cyanobacteria
and aerobic heterotrophic bacteria, shows a special capability in hydrocarbons
degradation (Abed et al. 2002; Cohen 2002; Abed and Koster 2005; Abed et al.
2006; Sanchez et al. 2005; Abed 2010; Goñi-Urriza and Duran 2018), probably due
to bacteria present in the microbial consortium (i.e., Marinobater and Alcanivoraxrelated members as well as species belonging to Rhodococcus, Sphingomonas,
Microbacterium genera) (Abed and Koster 2005). Microalgae and cyanobacteria
could participate to hydrocarbons degradation by performing biotransformation of
aromatic compounds into their hydroxylated intermediates that can be more easily
degraded by bacteria. Although they are not able to totally degrade pollutants, they
208
R. Denaro et al.