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ABSTRACT:In a continuing effort to develop inexpensive source tracking methods to detect human fecal contamination in environmental waters, targeted sampling was combined with fluorometry. Targeted sampling works by identifying hot spots of fecal contamination through multiple samplings over ever-decreasing distances. Fluorometry identifies human fecal contamination by detecting optical brighteners, primarily from laundry detergents. Because organic matter fluoresces and interferes with fluorometry, two locations were chosen for sampling: waters relatively low in organic matter at Mayagiiez Bay, Puerto Rico, and waters relatively high in organic matter at St. Simons Island, Georgia. In Puerto Rico, targeted sampling and fluorometry quickly and easily identified two hot spots of human fecal contamination in the Yagiiez River, which flows through the city of Mayagiiez. Another source tracking method, detection of the esp gene, confirmed their human origin. On St. Simous Island, targeted sampling and fiuorometry identified two hot spots of potential human fecal contamination. Detection of the esp gene confirmed the human origin of one site but not the other, most likely because background organic matter fluorescence interfered with fhiorometry. A separate experiment showed that adding a 436-um emission filter to the fluorometer reduced this background fluorescence by > 50%. With the 436-nm Filter in place, another sampling was conducted on St. Simons Island, and the second hot spot was identified as fecal contamination from birds. As long as the fluorometer was equipped with a 436-nm filter and organic matter concentrations were considered, targeted sampling combined with fluorometry was a relatively inexpensive method for identifying human fecal contamination in water.

Polymers containing nitrophenyl groups were isolated when P. oleovorans was grown with 5-(2′,4′-dinitrophenyl)valeric acid (DNPVA). Growth experiments were carried out containing variable ratios of this and nonanoic acid (NA). These revealed a loss of the 2′-nitro group as the experiment proceeded. The bacteria produced polymeric materials with 1.2%-6.9% of repeating units containing 4′-nitro and/or 2′,4′-nitrophenyl rings, depending on the DNPVA:NA molar ratio and total concentration of these carbon sources, according to NMR analysis. The polymeric material isolated from approximately 15% dry cell weight when using a 7:3 DNPVA:NA molar ratio at 10 mM total concentration was a yellow, elastic substance. Thermal analysis indicated the presence of two T g values, Tg,1 ) -35.95 °C and Tg,2 ) 28.74 °C, and one Tm value of 56.42 °C. These data suggest the presence of two polymers, one which contains nitrophenyl rings and the other being the copolymer of nonanoic acid.

Strains ofRhizobium forming nitrogen-fixing symbioses with common bean were systematically examined for the presence of the uptake hydrogenase (hup) structural genes and expression of uptake hydrogenase (Hup) activity. DNA with homology to the hup structural genes ofBradyrhizobiumjaponicum was present in 100 of 248 strains examined. EcoRI fragments with molecular sizes of approximately 20.0 and 2.2 kb hybridized with an internal SacI fragment, which contains part of both bradyrhizobial hup structural genes. The DNA with homology to the hup genes was located on pSym of one of the bean rhizobia. Hup activity was observed in bean symbioses with 13 of 30 strains containing DNA homologous with the hup structural genes. However, the Hup activity was not sufficient to eliminate hydrogen evolution from the nodules. Varying the host plant with two of the Hup+ strains indicated that expression of Hup activity was host regulated, as has been reported with soybean, pea, and cowpea strains.