FERMENTING OIL . THE MICROBIOLOGY OF SALTY OIL - Microbial Processes in Oil Fields: Culprits, Problems, and Opportunities Noha Youssef, Mostafa S. Elshahed, and Michael J. McInerney

Few studies have focused on isolating fermentative microorganisms from oil
reservoirs with elevated salinities.
 Fermentative halophilic oil reservoir isolates exclusively belong to the genus Haloanaerobium
(Order Haloanaerobiales) such as H. acetethylicum, H. salsuginis, H. congolese, and
H. kushneri (Bhupathiraju et al., 1994, 1999; Ravot et al., 1997).
Most Haloanaerobium spp. are saccharolytic and proteolytic, and produce H2, acetate,
and CO2 as end products of fermentation.
In spite of the general metabolic and phylogenetic diversity of mesophilic
fermentative microorganisms, few isolates that belong to this metabolic
group have been recovered from oil fields. In general, studies on the
isolation of mesophilic fermentative microorganisms from oil fields are
extremely sparse and are far from adequate to identify any global distribution
patterns or link members of any of the identified phylogenetic
groups to a specific ecological role in oil reservoirs.
Fermentative, mesophilic Firmicutes-affiliated isolates include Fusibacter paucivorans
, a new genus belonging to the order Clostridiales that utilizes a limited number
of carbohydrates and was isolated from an offshore oil field in Congo
(Ravot et al., 1999), Dethiosulfovibrio peptidovorans a proteolytic microorganism
that grows on peptones and individual amino acids but not
sugars (Magot et al., 1997b), and ‘‘Acetobacterium romashkovi,’’
 an acetogenic microorganism that is also capable of fermenting sugars and amino
acids (Davydova-Charakhch’yan et al., 1992b). In addition to Firmicutes, a
novel species within the genus Spirochaeta has been identified from oil
reservoirs (Magot et al., 1997a). A novel genus (Petrimonas) within the
phylum Bacteroidetes has recently been isolated from oil