Survival potential of Escherichia coli and Enterococci in subtropical beach sand: implications for water quality managers

Fecal bacteria have traditionally been used as indicator organisms to monitor the quality of recreational waters. Recent work has questioned the robustness of traditional indicators, particularly at seawater bathing beaches. For example, a study of Florida beaches found unexpectedly high abundances of Escherichia coli, fecal coliforms, and enterococci in beach sand. The aim of the present study was to explain these abundances by assessing the survival of E. coli and enterococci in beach sand relative to seawater. We used a combination of quantitative laboratory mesocosm experiments and field observations. Results suggested that E. coli and enterococci exhibited increased survivability and growth in sand relative to seawater. Because fecal bacteria are capable of replicating in sand, at least under controlled laboratory conditions, the results suggest that sand may be an important reservoir of metabolically active fecal organisms. Experiments with "natural" mesocosms (i.e., unsterilized sand or water rich in micropredators and native bacteria) failed to show the same increases in fecal indicators as was found in sterile sand. It is postulated that this was due to predation and competition with indigenous bacteria in these "natural" systems. Nonetheless, high populations of indicators were maintained and recovered from sand over the duration of the experiment as opposed to the die-off noted in water. Indicator bacteria may wash out of sand into shoreline waters during weather and tidal events, thereby decreasing the effectiveness of these indicators as predictors of health risk and complicating the interpretations for water quality managers.     

Relatedness among nestmates in a primitively social wasp,Cerceris antipodes (Hymenoptera: Sphecidae)

Summary Kin selection, acting through high levels of relatedness, may be an important promoter in the evolution of nest sharing. Cerceris antipodes is a sphecid wasp that shares nests in contrast to the majority of sphecids where only one female occupies a nest. Nest sharing results from females remaining in their natal nests and females moving to already occupied nests. Average relatedness among nestmates of C. antipodes was calculated from allele frequencies of phosphoglucomutase to determine whether nests were usually shared by close relatives. Relatedness among nestmates was high (0.5 to 0.6) at one aggregation in two consecutive years. Preferential association of relatives away from the natal nest can be inferred from these high values combined with the frequency of nest switching observed. Estimates of relatedness were lower (about 0.3) and associated with large standard errors at 3 other aggregations. Inbreeding and relatedness between neighbouring nests were only significant at the aggregation with the fewest females. This may be a result of the small effective population size. The levels of relatedness observed are consistent with kin selection through relatedness being an important factor in the evolution of nest sharing.     

Prenatal diagnosis of trisomy 21 and X/XX sex chromosome mosaicism

Double aneuploidy involving Down syndrome and Turner syndrome is a rare chromosomal abnormality presumed to occur with a frequency of about 1 in 2 million births. Twenty-one cases of this combined anomaly have been reported and two infants were born with this anomaly after a mistake in prenatal diagnosis. We report the first prenatal diagnosis of Down syndrome combined with Turner mosaicism and suggest that this polysyndrome may be more common than previously estimated. We, therefore, wish to alert cytogenetic laboratories performing prenatal diagnoses of the potential risks of misdiagnosis of this polysyndrome if banding is not performed and if a sufficient number of mitotic cells are not analysed.