 Ahmad Thontowi, Nanik Rahmani and Yopi
Oil spills are also now becoming a frequent and major source of water
and coastal contamination (US Environmental Protection Agency, 1990).
Around five million tons of crude oil and refined oil enter the
environments each year as a result of anthropogenic source such as oil
spills (Hinchee and Kitte 1995). Petroleum is complex mixture
of many
compounds mainly consisting of carbon and hydrogen which potentially
could be eliminated by microbial degradation.
Crude oil constituents are classified into four fractions: saturates
(alkane), aromatics, resins and asphaltenes. Each of these fractions
contains a large number of compounds. Polycyclic aromatic hydrocarbons
(PAHs) are a class of fused-ring aromatic compounds that are ubiquitous
environmental pollutants (Fernandez et al. 1999). Microorganisms play an
important role in the degradation of PAHs in terrestrial and aquatic
ecosystems, and microbial degradation is the main process in natural
decontamination. Enhancement of this phenomenon is the basis of
bioremediation technologies (Alexander 1999).
PAHs are a group of persistent, toxic, mutagenic and carcinogenic
pollutants which pose a significant risk to human health and the
environment (Menzie et al. 1992). They are converted to cis-dihydrodiols
by bacterial dioxygenase, an enzymatic system consisting of ferredoxin,
ferredoxin reductase, and a terminal ring-hydroxylating dioxygenase
composed of a and b (Cerniglia 1992). The a subunit of the terminal
dioxygenase is more conservative than other components and is thought to
be critical for substrate recognition (Kauppi et al. 1998). Evaluating
the particular gene expressing this subunit could improve our
understanding of the genetics of PAH-degrading bacteria and assist in
monitoring active microbial communities during bioremediation (Habe
& Omori 2003; Dionisi et al. 2004).
 Several
reports about the isolation of PAH-degrading bacteria and the
biochemical and genetic analyses of PAH degradation have been cited
(Cerniglia 1992). During the research time about diversity bacteria and
functional genes in PAHs hydrolysis have conducted in subtropical sea.
In the tropical sea environment, especially in Indonesia have been
little reported (Widada et al. 2002; Harwati et al. 2007).
We have been reported diversity of oil-degrading bacteria from Muara
Kamal Jakarta bay (Yopi et al. 2006). These bacteria have been known as
alkane degrader (Thontowi et al. 2008), but have not been known their
ability on PAHs degradation. From the bacteria collection expected can
be obtained PAHs degrading bacteria. It is important of knowing the
ability of PAHs degrading bacteria. In this case for the specific
compound in PAHs. Besides that, the applications of dioxygenase enzyme
for industry like polyphenylene (Romero et al. 2005), paint (indigo)
(O'Connor et al. 1997), as well as an HIV disease inhibitor (Indivanir)
(Gibson & Parales 2000; Boyd & Sheldrake 1998) very
interestingly.
The aims of this research were selected and characterized
PAHs-degrading bacteria, identified of potential PAHs degrading bacteria
by partial analysis of 16S rDNA gene, and analyzed the diversity of
PAHs-degrading gene from Indonesian sea water bacteria. From the
expected targets to be obtained, bacteria and their character in
PAHs-degrading activities, detected and data base form diversity of
PAHs-degrading gene.
The eighteen bacteria from Indonesia Sea Water were analyzed base on
partial sequence 16S rDNA gene, Polyaromatic hydrocarbons (PAHs)
degradation ability and analyzed of PAHs dioxygenase gene. Homology
analysis of partial 16SrDNA gene from 18 strain PAHs (phenanthrene,
dibenzothiopene, fluorene, fluoranthene, phenothiazine and pyrene)
degrader were acquired 14 genus bacteria and classified into two groups,
a and g-proteobacteria (Fig 2). Phenantrene degradation result was
remaining 10.5% after 4 days cultivation by strain 18. Dibenzothiophene
degradation result was remaining 22% after 4 days cultivation by strain 5
(Fig 3). The sequences of PAHs dioxygenase gene of strain 5 and 8
showing 98 and 99% respectively identity with naphthalene dioxygenase
gene from gene bank (Table 1).
| Table 1. Sequence Homology of PAH Dioxygenase |
Isolate number
|
Most similar 16S rDNA sequence
|
Sequence producing significant alignment
|
%
|
5
|
Pseudoalteromonas sp. KT 0812A |
naphthalene dioxygenase |
98 |
8
|
Marinobacter hydrocarbonoclasticus |
naphthalene dioxygenase |
99 |
From the results study bacteria and their character in PAHs-degrading
activities, detected and data base form diversity of PAHs-degrading
gene, we can manage of bioremediation and biomonitoring oil pollution.
This research assumed that functional genes encode for specific enzymes
in catabolic pathways such as key enzymes in xenobiotic degradation
pathways. By assessing the abundance or the expression of key genes in
environmental samples one can get a potential measure of the degradation
activity. One way of assessing the abundance and expression of specific
catabolic genes is by analyzing the metagenomic DNA and RNA from
environmental samples. |
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