BACKGROUND: Bioremediation is emerging as an attractive means to
restore inaccessible or environmentally sensitive areas. The degradation of
spilled hydrocarbons is one application where the seeding of bacteria is
particularly attractive since it is the microbes who ultimately consume and
remove these materials, whether they occur naturally (as in marsh plant
cuticles) or as an anthropogenic input. Increasingly we are seeing technological
developments in which fluids of diverse origins are brought together, either by
design or by accident. We are seeing renewed interest in the use of
bioremediation for the purpose of remediatiing spilled oil.
OBJECTIVES: Methods used by the molecular biologist were utilized to,
1) quantitatively amplify the DNA of target species, and 2) develop molecular
probes that would unequivocally and rapidly identify the test species. The
upshot of these efforts was the development of a methodology that may be used to
assess changes in any microbial assemblage as a result of changes in the
ecosystem, or for tracking introduced microbial species during bioremediation
efforts.
DESCRIPTION: In general, bioremediation consists of either seeding
bacteria that have been adapted in the laboratory to rapidly degrade the
material in question, or modification of the environment with ‘fertilizers" to
promote the development of natural microbial assemblages that are associated
with the contaminant. The seeded bacteria might begin the degradation process
immediately and more efficiently, whereas fertilizer addition might entail a
relatively long lag period before effects are seen. The critical question,
however, is whether the seeded microbes can compete and survive against native
species in a foreign environment.
SIGNIFICANT CONCLUSIONS: A new species of Acinetobacter that is
capable of using hexadecane as its sole carbon source was isolated from coastal
wetlands in Louisiana. When laboratory grown cultures of the Acinetobacter were
re-introduced to an experimental flow-through marsh environment and hexadecane
added, the microbe quickly displaced all other bacteria and represented
essentially 99% of the microbial community. When Acinetobacter was added to
Mississippi River water supplemented with hexadecane in a chemostat, it was
completely displaced after six days at which time an indigenous microflora
developed that reached a community density of 2 x 10 6 CFU per ml. One of the
controls in tis experimen was simply the addition of hexadecane to a chemostat
that had only river water passed through it, and a microbial community of
approximately 106 developed right from the start.
STUDY RESULTS: The results are that 1) Seed bacteria may readily be
introduced back into the environment from which they originated, 2) Seed
bacteria do not necessarily survive in foreign environments, and 3) Seeded
bacteria may actually inhibit the development of normal microflora capable of
utilizing the contaminating material. A methodology was developed that may be
used to assess changes in any microbial assemblages as a result of changes in
the ecosystem, or for tracking introduced microbial species during
bioremediation efforts.
STUDY PRODUCTS: LaRock, P.A. and L.S. Donovan. 2001. Survival of a
hydrocarbon-utilizing bacterium when introduced into native and foreign
environments. US Dept. of the Interior, Minerals Management Service, Gulf of
Mexico OCS Region, New Orleans LA. OCS Study MMS 2001-094. 52 pp.
STUDY TITLE: Survival of a hydrocarbon-utilizing bacterium when
introduced into native and foreign environments
REPORT TITLE: Survival of a hydrocarbon-utilizing bacterium when
introduced into native and foreign environments
CONTRACT NUMBER(S): 14-35-001-30660-19921
SPONSORING OCS REGION: Gulf of Mexico OCS Region
APPLICABLE PLANNING AREA(S): Gulf of Mexico
FISCAL YEAR(S) OF PROJECT FUNDING: 1994 - 2001
COMPLETION DATE OF REPORT: December 2001
COST(S): FY 1994; $167,774: CUMULATIVE PROJECT COST: $167,774
PROJECT MANAGER(S): Paul A. LaRock and Lisa S. Donovan
AFFILIATION: Louisiana State University
ADDRESS: Department of Oceanography and Coastal Sciences, School of
the Coast and Environment, Baton Rouge, LA 70803
PRINCIPAL INVESTIGATOR(S)*: Paul A. LaRock and Lisa S. Donovan
KEYWORDS: bioremediation, hydrocarbon degradation, PCR probe, PCR
primer, fluorescence, bacteria
