pattern of substrates, in pristine marine sites. In addition, the ability to adsorb and
accumulate polycyclic aromatic hydrocarbons molecules from the surrounding seawater by algae would create a polycyclic aromatic hydrocarbons enriched zone
around the phytoplankton cell surface, where polycyclic aromatic hydrocarbonsdegrading bacteria can proliferate (Gutierrez and Aitken 2014). Such association was
proved to be also functional for polycyclic aromatic hydrocarbons removal, particularly during periods of bloom. With special attention to bioremediation, algae–
bacteria consortia seem to enhance the rate of biodegradation processes. For
instance, the alga Chlorella sorokiniana associated with Pseudomonas migulae
(Munoz et al. 2003), as well as microalgaeSelenastrum c. and Mycobacterium
sp. (Luo et al. 2014) exhibit best performance in the degradation of hydrocarbons
than algae or bacteria alone. Synechocystis sp. coupled with Pseudomonas sp. and
Bacillus sp. showed an enhancement of the growth rate together with an ameliorated
capability in the polycyclic aromatic hydrocarbon degradation (Patel and Hellgardt
2015). Tang et al. (2012) demonstrated that a microalgal–bacterial consortium
formed by one axenic Scenedesmus obliquus and four hydrocarbon-degrading
bacteria was able to reduce the aromatic hydrocarbons contamination faster than
bacterial consortium alone.
Marine microalgal extracellular polymeric substances can contain many complex
nonpolar molecules (e.g., poly-unsaturated fatty acids) incorporated into macromolecular protein/lipid/polysaccharide matrices (Flemming et al. 2007; Dewapriya and
Kim 2014; Neu and Lawrence 2016). Potential complexation of petroleum hydrocarbons to extracellular polymeric substances molecules would influence distribution/partitioning and therefore the fate of hydrocarbons (Sikkema et al. 1995;
Kalmykova et al. 2013). Gutierrez et al. (2013) and Quigg et al. (2016) argue the
role of marine oil snow (MOS) upon the in situ biodegradation processes. In fact, the
aggregates of hydrocarbonoclastic bacteria and phytoplankton, kept together by
bacterial-produced extracellular polymeric substances, sink along water column as
flocculent accumulation to the seafloor where the rate of catalyses could be significantly slowed down due to environmental constraints (pressure, temperature, and
oxygen). Extracellular polymeric substances produced by another algal-associated
oil-degrading bacterium (Halomonas) exhibit trace metal binding capacities (Ca, Fe,
Mn, Mg, Al) and may be involved in nutrient sharing between bacteria and
microalgae (Gutierrez et al. 2012).
It is also noticeable that the oil-resisting consortia show a decrease in biodiversity
due to the toxic effect of oil. Parsons and coauthors (2015) showed that after the
Deepwater Horizon oil-spill, diatoms and cyanobacteria dominated the survivor
phytoplankton. The differential behavior is likely species-dependent and could be
expressed as different tolerance to oil (Ozhan and Bargu 2014), or different biodegradation capability (Prouse et al. 1976; Jung et al. 2012; Parsons et al. 2015). In a
recent microcosm study, phytoplankton-associated bacterial community showed an
improvement on degradation capability when bacteria were associated to phytoplankton (Thompson et al. 2017). Also, bacteria associated with the mucilaginous
sheath/capsule of cyanobacteria show interesting biodegradation capability
(Sorkhoh et al. 1995; Radwan et al. 2002; Abed and Koster 2005; Chaillan et al.
2006). Al-Hasan et al. (1998) identified four genera of heterotrophic bacteria
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R. Denaro et al.
accumulate polycyclic aromatic hydrocarbons molecules from the surrounding seawater by algae would create a polycyclic aromatic hydrocarbons enriched zone
around the phytoplankton cell surface, where polycyclic aromatic hydrocarbonsdegrading bacteria can proliferate (Gutierrez and Aitken 2014). Such association was
proved to be also functional for polycyclic aromatic hydrocarbons removal, particularly during periods of bloom. With special attention to bioremediation, algae–
bacteria consortia seem to enhance the rate of biodegradation processes. For
instance, the alga Chlorella sorokiniana associated with Pseudomonas migulae
(Munoz et al. 2003), as well as microalgaeSelenastrum c. and Mycobacterium
sp. (Luo et al. 2014) exhibit best performance in the degradation of hydrocarbons
than algae or bacteria alone. Synechocystis sp. coupled with Pseudomonas sp. and
Bacillus sp. showed an enhancement of the growth rate together with an ameliorated
capability in the polycyclic aromatic hydrocarbon degradation (Patel and Hellgardt
2015). Tang et al. (2012) demonstrated that a microalgal–bacterial consortium
formed by one axenic Scenedesmus obliquus and four hydrocarbon-degrading
bacteria was able to reduce the aromatic hydrocarbons contamination faster than
bacterial consortium alone.
Marine microalgal extracellular polymeric substances can contain many complex
nonpolar molecules (e.g., poly-unsaturated fatty acids) incorporated into macromolecular protein/lipid/polysaccharide matrices (Flemming et al. 2007; Dewapriya and
Kim 2014; Neu and Lawrence 2016). Potential complexation of petroleum hydrocarbons to extracellular polymeric substances molecules would influence distribution/partitioning and therefore the fate of hydrocarbons (Sikkema et al. 1995;
Kalmykova et al. 2013). Gutierrez et al. (2013) and Quigg et al. (2016) argue the
role of marine oil snow (MOS) upon the in situ biodegradation processes. In fact, the
aggregates of hydrocarbonoclastic bacteria and phytoplankton, kept together by
bacterial-produced extracellular polymeric substances, sink along water column as
flocculent accumulation to the seafloor where the rate of catalyses could be significantly slowed down due to environmental constraints (pressure, temperature, and
oxygen). Extracellular polymeric substances produced by another algal-associated
oil-degrading bacterium (Halomonas) exhibit trace metal binding capacities (Ca, Fe,
Mn, Mg, Al) and may be involved in nutrient sharing between bacteria and
microalgae (Gutierrez et al. 2012).
It is also noticeable that the oil-resisting consortia show a decrease in biodiversity
due to the toxic effect of oil. Parsons and coauthors (2015) showed that after the
Deepwater Horizon oil-spill, diatoms and cyanobacteria dominated the survivor
phytoplankton. The differential behavior is likely species-dependent and could be
expressed as different tolerance to oil (Ozhan and Bargu 2014), or different biodegradation capability (Prouse et al. 1976; Jung et al. 2012; Parsons et al. 2015). In a
recent microcosm study, phytoplankton-associated bacterial community showed an
improvement on degradation capability when bacteria were associated to phytoplankton (Thompson et al. 2017). Also, bacteria associated with the mucilaginous
sheath/capsule of cyanobacteria show interesting biodegradation capability
(Sorkhoh et al. 1995; Radwan et al. 2002; Abed and Koster 2005; Chaillan et al.
2006). Al-Hasan et al. (1998) identified four genera of heterotrophic bacteria
212
R. Denaro et al.