Determination of In Situ Bacterial Growth Rates in Aquifers and Aquifer Sediments

Abstract

Laboratory and field-scale studies with stained cells were performed to monitor cell growth in groundwater systems. During cell division, the fluorescence intensity of the protein stain 5-(and 6-)-carboxyfluorescein diacetate succinimidyl ester (CFDA/SE) for each cell is halved, and the intensity can be tracked with a flow cytometer. Two strains of bacteria, Comamonas sp. strain DA001 and Acidovorax sp. strain OY-107, both isolated from a shallow aquifer, were utilized in this study. The change in the average generation or the average fluorescence intensity of the CFDA/SE-stained cells could be used to obtain estimates of doubling times. In microcosm experiments, the CFDA/SE-based doubling times were similar to the values calculated by total cell counting and were independent of cell concentration. Intact and repacked sediment core experiments with the same bacteria indicated that changes in groundwater chemistry were just as important as growth rates in determining planktonic cell concentrations. The growth rates within the sediment cores were similar to those calculated in microcosm experiments, and preferential transport of the daughter cells was not observed. The experiments indicated that the growth rates could be determined in systems with cell losses due to other phenomena, such as attachment to sediment or predation. Application of this growth rate estimation method to data from a field-scale bacterial transport experiment indicated that the doubling time was approximately 15 days, which is the first known direct determination of an in situ growth rate for bacteria in an aquifer.

Absence of Spiroplasma or Other Bacterial 16S rRNA Genes in Brain Tissue of Hamsters with Scrapie

“…Once the code was broken, the sample that produced this product proved to be an uninfected sample, and the S. mirum sequence was judged to result from an inadvertent contamination with the positive control S. mirum spike. None of the other cloned sequences matched sequences from any mollicutes, but they were homologous to 16S rRNA gene sequences from a variety of known and unknown bacteria, including Acidovorax, Variovorax, and Aquaspirillum, bacterial species which are naturally found in environmental water sources and which can be isolated from purified water systems (29,13,34,30). These sequences were found as frequently in uninfected samples as in infected samples and only after 70 cycles of amplification.…”

Microbial diversity in biofilms from corroding heating systems

“…The possibility that Acidovorax were responsible for at least part of the corrosion seen in the DH systems has been demonstrated in studies of copper plumbing (Critchley et al 2003). In addition, members of the genus Acidovorax have been found in a variety of potentially corrosive environments including aerobic, ironreducing and anaerobic environments (Johnson et al 2001;Rö ling et al 2001;Mailloux & Fuller, 2003). Acidovorax have also been shown to be very efficient in degrading complex organic substances such as PCBs (poly chlorinated biphenyls) and PAHs (polycyclic aromatic hydrocarbons) (Zhao & Ward, 1999;Eriksson et al 2003), nitrobenzene (Etchebere et al 2001), plastics (Uchida et al 2000;Wang & Lee, 2001), phenols (Watanabe et al 2002) or chloroanilines (Boon et al 2003).…”

Linking environmental heterogeneity and reproductive success at single-cell resolution

“…Thus, the GFP content of an individual offspring cell becomes a quantifiable measure of reproductive success. This approach resembles the method that was used (Mailloux and Fuller, 2003) to estimate in situ doubling times for bacteria released into an aquifer after staining them with carboxyfluorescein diacetate succinimidyl ester, a fluorescent protein stain that dilutes from the bacteria with every cell division. However, whereas these authors were interested solely in population averages of in situ growth, we tested our GFP-based bioreporter by exposure to microscopic conditions of low (that is, LB broth) and high (that is, the phyllosphere) environmental heterogeneity to reveal sub-population differences in the reproduction of single bacteria.…”