WP20 Contaminated Harbor and River Sediment
Wednesday, 16 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall

(GOM-1117-811357) Aerobic Transformation of Polychlorinated Biphenyls by Microorganisms Isolated from Sediments of the San Jose Lagoon.

Gomez-Alvarez, V^{1, 2}, Toranzos, G², ¹ University of Massachusetts, Amherst, MA, USA² University of Puerto Rico, San Juan, PR, USA

ABSTRACT- Polychlorinated biphenyl compounds (PCBs) are distributed worldwide, and in many cases sediments act as ultimate sinks for this man-made pollutant. PCBs have captivated concern because of their persistence and possible health effects. Little is known about the PCB-utilizing microbial communities in tropical sediments. The objectives of this project were: (i) isolate and enumerate aerobic bacteria capable of transforming PCBs from sediments of the San Jose lagoon (Puerto Rico), (ii) determine their PCB-degradative competence, and (iii) measure the transformation of PCBs by mixed bacterial communities using sediment microcosms. An understanding of the biodegradative capacity of populations by individual bacteria as well as communities of bacteria is important in understanding PCB's biodegradation in tropical environments. DNA-DNA hybridization determined the presence of PCB-degrading gene in our sediments. Furthermore, less than 0.000001% of the total recoverable aerobic bacterial populations were biphenyl-degrading. Indigenous aerobic bacteria capable of transforming PCBs were isolated using biphenyl enrichment cultures. PCBs have been shown to be co-metabolized by the microbiota when biphenyl is present. Six isolates were selected to determinate PCB-degrading competence of a mixture of six congeners and Aroclor 1248. All isolates transformed the detectable mono-, di-, and trichlorobiphenyls and most of the tetra- and pentachlorobiphenyls. Microcosm assays demonstrated the abilities of the indigenous microbiota of the sediment amended with biphenyl to transform several congeners of PCBs in sediments. The lower-substituted congeners were degraded more rapidly and congeners with the same amount of chlorine were transformed at different rates. Variations in microbial communities during biodegradation of PCBs were monitored using carbon source profiles. Principal Component Analysis revealed a distinction between disturbed (PCBs) and undisturbed sediment samples. PCBs may affect the physiological diversity of the communities. In conclusion the indigenous tropical microbiota may have the potential to degrade PCBs present in the lagoon sediments.

Key words: PCB, Sediments, Microorganisms, Microcosms