chronological events. An early stage, which occurs over days, is characterized by
spreading, evaporation, dispersion, emulsification, and dissolution. Diversely, at
later stage, oxidation, sedimentation, and biodegradation occur over years, determining the ultimate fate of the oil spilled (Harayama et al. 1999; Dutta and
Harayama 2001). Each fraction of crude oil has different behavior in marine
environment: hydrocarbons having lower molecular weight form slicks on the
surface and are subjected to spreading, mixing, and volatilization/evaporation
whereas heavier resins form persistent tar balls with low surface area. The effect
of mixing, but even more tension-active substances produced by microorganisms
(biosurfactants), creates emulsions that are more easily degradable (Harayama et al.
1999; Yamada et al. 2003; Xue et al. 2015; Atlas and Hazen 2011). Sunlight
radiation causes photo-oxidation of floating petroleum hydrocarbon molecules and
in presence of algae the response of microbial community to oil is differently
modulated (Medina-Sánchez et al. 2002; Aksmann and Tukaj 2008; Huang et al.
2014; Bacosa et al. 2015).
Processes occurring during the early phase result in the partitioning of oil
components among the sea surface, air, water column, and sediments. After extensive alterations, however, many petroleum hydrocarbons persist unchanged and
consequently their toxicity is diluted but not diminished. Petroleum residues,
asphaltenes, and nonvolatile hydrocarbons persist indefinitely. Natural occurring
biological and chemical degradation processes become increasingly significant
over months. Because marine microorganisms ingest, metabolize, and utilize the
petroleum as a carbon source, petroleum hydrocarbons and residues in the environment do not exist in greater abundance. Without microorganisms, the abundance of
hydrocarbons would increase at possibly undesirable rates. Isolation and identification of microorganisms responsible for hydrocarbon transformations have long been
acknowledged and include bacteria, yeasts, fungi, and algae (Atlas 1981; Leahy and
Colwell 1990; Atlas and Cerniglia 1995). The biodegradation efficiency was shown
to range from 6% to 82% for soil fungi (Bovio et al. 2017), from 0.13% to 50% for
soilbacteria (Jones et al. 1970), and from 0.003% to 100% for marine bacteria
(Mulkins-Phillips and Stewart 1974).
The use of microbial community for the recovery of impacted marine areas is the
subject of bioremediation, a biotechnology mainly targeted to exploit processes
carried out by single type of microorganisms. Indeed, hydrocarbons degradation
processes in the natural environment are too complicated to be entirely
comprehended, and therefore a system biology approach is required to investigate
networks and interaction at the molecular, cellular, and ecosystem levels.
In this chapter, we outline the existing knowledge about the interaction between
bacteria and algae during the petroleum biodegradation process; whereafter, we will
specifically focus on the bacterial and algal actions under aerobic conditions.
198
R. Denaro et al.
spreading, evaporation, dispersion, emulsification, and dissolution. Diversely, at
later stage, oxidation, sedimentation, and biodegradation occur over years, determining the ultimate fate of the oil spilled (Harayama et al. 1999; Dutta and
Harayama 2001). Each fraction of crude oil has different behavior in marine
environment: hydrocarbons having lower molecular weight form slicks on the
surface and are subjected to spreading, mixing, and volatilization/evaporation
whereas heavier resins form persistent tar balls with low surface area. The effect
of mixing, but even more tension-active substances produced by microorganisms
(biosurfactants), creates emulsions that are more easily degradable (Harayama et al.
1999; Yamada et al. 2003; Xue et al. 2015; Atlas and Hazen 2011). Sunlight
radiation causes photo-oxidation of floating petroleum hydrocarbon molecules and
in presence of algae the response of microbial community to oil is differently
modulated (Medina-Sánchez et al. 2002; Aksmann and Tukaj 2008; Huang et al.
2014; Bacosa et al. 2015).
Processes occurring during the early phase result in the partitioning of oil
components among the sea surface, air, water column, and sediments. After extensive alterations, however, many petroleum hydrocarbons persist unchanged and
consequently their toxicity is diluted but not diminished. Petroleum residues,
asphaltenes, and nonvolatile hydrocarbons persist indefinitely. Natural occurring
biological and chemical degradation processes become increasingly significant
over months. Because marine microorganisms ingest, metabolize, and utilize the
petroleum as a carbon source, petroleum hydrocarbons and residues in the environment do not exist in greater abundance. Without microorganisms, the abundance of
hydrocarbons would increase at possibly undesirable rates. Isolation and identification of microorganisms responsible for hydrocarbon transformations have long been
acknowledged and include bacteria, yeasts, fungi, and algae (Atlas 1981; Leahy and
Colwell 1990; Atlas and Cerniglia 1995). The biodegradation efficiency was shown
to range from 6% to 82% for soil fungi (Bovio et al. 2017), from 0.13% to 50% for
soilbacteria (Jones et al. 1970), and from 0.003% to 100% for marine bacteria
(Mulkins-Phillips and Stewart 1974).
The use of microbial community for the recovery of impacted marine areas is the
subject of bioremediation, a biotechnology mainly targeted to exploit processes
carried out by single type of microorganisms. Indeed, hydrocarbons degradation
processes in the natural environment are too complicated to be entirely
comprehended, and therefore a system biology approach is required to investigate
networks and interaction at the molecular, cellular, and ecosystem levels.
In this chapter, we outline the existing knowledge about the interaction between
bacteria and algae during the petroleum biodegradation process; whereafter, we will
specifically focus on the bacterial and algal actions under aerobic conditions.
198
R. Denaro et al.