However, there are many sources of oil pollution in the ocean other than
tanker and oil rig accidents. Human activity on the land and natural seeps
as well as municipal and industrial waste discharge. Progress in
bioremediation have allowed the discovery of a fascinating new group of
marine bacteria, namely the hydrocarbonoclastic bacteria (HCB), that play
a critical role in the natural cleansing of marine systems and obviously
have a biotechnological potential. The HCB are marine obligate bacteria,
ubiquitous in the ocean environments and highly representative in the oil
polluted areas, that use only a few hydrocarbons and few low-molecular
weight organic acids as carbon source.
Due to their very high affinity for the hydrocarbons, and to their
autochthonous origin, the HCB offer a great opportunity for natural
attenuation of the polluted marine environments with no significant
adverse impact. The Istituto per l'Ambiente Marino Costiero sezione di
Messina (IAMC-ME) is actively working on the study of the HCB distribution
overall the word oceans, and their genetic and physiological
characterisation as well as the improvement of their use for
bioremediation. For such an aim, IAMC-ME is leading several national and
international projects. Within these framework, the Sicilian coastlines
have been mapped for the detailed distribution of different HBC taxa, by
means of semiquantitative analyses of HCB target genes, and several HCB
isolates specialised in the degradation of medium-chain alkanes (m-c alk)
have been already described. Among these isolates, the new genera
Alcanivorax (the genome of which has been completely sequenced),
Oleiphilus, Thalassolituus, and Oleispira have been described in peer-
reviewed published articles (Figure 1), the last one exhibiting
pyscrophilic behaviour (temperature optima between 2-4 °C) and the unusual
composition of the cell-membrane with a high percent of polyunsaturated
fatty acids (PUFA) and the capability to synthesize eicosapentaenoic acid
(EPA) of commercial interest. Microcosms experiments for evaluating the
potential of HCB for bioremediation have been set up and the results
showed the very fast response of local bacterial natural communities to
the oil addition in presence of optimal concentration of nutrients with
relative abundance of HCB taxa increasing within the first 10 to 15 days
up to the 90% of the total bacterial numbers. This was bringing to the
rapid degradation of m-c alk components of the crude oil, previous
emulsification of the oil due to the HCB bioemulsifier production (Figure
2). Bioaugmentation (by seeding the natural consortia with optimal
densities of selected HCB active cells) experiments in medium scale
(mesocosms) are planned for the next future.
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