Daniel H. Pope

Growth ofLegionella pneumophila in two-membered cultures with green algae and cyanobacteria

Environmental and clinical isolates ofLegionella pneumophila were grown in minimal-salts media (no organic compounds added) in associated with various green algae and cyanobacteria. Growth was observed to level off after a period of hours to days with no subsequent significant loss in the numbers of viableL. pneumophila even several days after growth had ceased. Transfer to new algal or cyanobacterial cultures resulted in a new burst of growty by theL. pneumophila.

Microbes in antarctic waters of the Drake Passage: Vertical patterns of substrate uptake, productivity and biomass in January 1980

SummaryMicrobial distribution, substrate uptake, productivity and biomass were investigated in the water column of the Drake Pasage, Antarctica. Organic substrate uptake and productivity were determined by the utilization of [14C] and [3H] glucose and by the incorporation of [3H] adenine and [3H] thymidine into RNA and DNA. Microbial biomass was estimated by ATP concentrations and bacterial abundance by epifluorescence direct counts. Estimates of glucose uptake and productivity indicate that microbes were most active in surface waters and least active below 100 m. Although glucose uptake was generally less than 10 ng/l·h, microbes maintained a low available glucose pool. Glucose concentrations varied from undetectable to 7.5 μg/l with a turnover time of 5–20 days in the euphotic zone and greater than 365 days in Circumpolar Deep Waters. Microbes respired 12 to 32% of the assimilated [14C] glucose. Microbes responsible for the uptake of dissolved organic cabon in the euphotic zone were in the <3 μm size class, presumably bacteria whereas in the aphotic zone the uptake of organics, albeit low, was due to microbes >3 μm, most likely on particles. Microbial ATP-biomass decreased rapidly with increasing water depth and most (∼60–70%) of the ATP-biomass was due to microbes >3 μm. Although bacterial numbers were high (>108 cells/l) at several stations, there were generally between 107 and 108 cells/l with increasing water depth. Bacterial biomass was estimated at <3% of the microbial biomass (7.3 gC/m2) in the euphotic zone. Conservative estimates of secondary productivity by microbes were between 0.5 and 3.0 mg C/m2·d (0.2–54 ng C/l·d).

Comparative effectiveness of chlorine and chlorine dioxide biocide regimes for biofouling control

The effectiveness of chlorine (Cl2) and chlorine dioxide (ClO2) in controlling biofouling of 304L stainless steel heat exchanger tubing was compared using an experimental trough system. Three combinations of dose and contact time were evaluated. Chlorination coupled with a dispersant was also tested. Three criteria were used to assess the degree of fouling; organic carbon and dry weight of the fouling material accumulated on metal specimens and the visual appearance of this material on the specimens. These parameters correlated well with one another and therefore, collectively provided an effective means of evaluating biocide efficacy. Metal specimens in all troughs receiving biocide treatment were much less fouled than those in the trough receiving no biocide. Continuous application of Cl2 at about 0.15 ppm was more effective than four 15-min 1 ppm Cl2 applications per day. Both of these treatment regimes were more effective than a dose of about 1 ppm for 1 h day−1. Use of a dispersant in combination with Cl2 showed no significant reduction in the amount of biofouling material accumulation, although a difference in the texture of this material was observed. Unlike the Cl2 results, low-level continuous ClO2 treatment at 0.15 ppm resulted in biofouling similar to that when 1 ppm of ClO2 was used for 1 h day−1. Overall, ClO2 was significantly (P < 0.05) more effective in controlling biofouling than Cl2.

Measure ofLegionella pneumophila activity in situ

Detection ofLegionella pneumophila by serogroup-specific fluorescent antibodies was combined with a tetrazolium dye (INT) to measure electron transport activity. The biological uptake and reduction of the INT dye was studied in pure cultures and in natural water samples with respect to temperature. Uptake was complete within 60 min. Controls inhibited with formaldehyde demonstrated little activity. Both the in vitro and in situ determinations suggested that the electron transport system ofLegionella was active over a temperature range of 25 to 60°C.

The effect of ozone onLegionella pneumophila and other bacterial populations in cooling towers

Ozone was found to reduce the numbers of bacteria detectable by plate counts and the numbers of presumptiveLegionella pneumophila (DFA-reactive cells), including those that were INT positive, in test cooling towers. The numbers of DFA-reactiveL. pneumophila eventually reached those of the makeup water (Troy, NY, city water). Microbial slime on the interior tower surfaces andPseudomonas populations in the tower waters were also reduced. Water chemistry parameters measured showed no tendency toward a condition that would cause accelerated deterioration of tower material.

Productivity and species composition of algal mat communities exposed to a fluctuating thermal regime

Algal mat communities growing in thermal effluents of production nuclear reactors at the Savannah River Plant, near Aiken, SC, are exposed to large temperature fluctuations resulting from reactor operations. Rates of primary production and species composition were monitored at 4 sites along a thermal gradient in a trough microcosm to determine how these large temperature fluctuations affected productivity and algal community structure. Blue-green algae (cyanobacteria) were the only phototrophic primary producers growing in water above 45°C. These thermophiles were able to survive and apparently adapt to ambient temperatures when the reactor was shut down. The algal mat communities exposed to <45°C were composed of blue-green and eukaryotic algae that adapted rapidly to ambient temperatures. An increase in the percentage extracellular release (PER) of14C-labeled dissolved organic compounds and a decrease in primary production were observed during periods of thermal fluctuation. The results show that the dominant phototrophs in this artificially heated aquatic habitat have been selected for their ability to survive large temperature fluctuations and are similar to those of natural hot springs.

Distribution and seasonality ofLegionella pneumophila in colling towers

The numbers of presumptiveLegionella pneumophila cells in waters and sediments of nine different cooling towers located on the same site in the northeastern United States were determined at approximately monthly intervals for 18 months. All systems received makeup water from the same source and received the same chemical treatments. PresumptiveL. pneumophila were found in both water and sediment samples from all systems on all sampling dates. An important result of this study was the finding that tower sediments represent large reservoirs ofL. pneumophila. The only correlation between levels of presumptiveL. pneumophila and any of the physical, chemical, or operating characteristics evaluated was with winter shutdown and drainage followed by a nonoperational period. These systems showed a definite seasonal response with the highest levels of presumptiveL. pneumophila found in the summer and fall. Systems operated year round showed relatively constant numbers ofL. pneumophila in both water and sediments.

Purification and characterization of low potential c cytochromes from Desulfovibrio desulfuricans membranes

Desulfovibrio desulfuricans grown in a lactate‐sulfate medium produces, in addition to soluble cytochromes, c‐type cytochromes which appear to be integral membrane proteins. Two cytochromes can be separated, an abundant 15 kDa cytochrome and a 22 kDa cytochrome. Both have optical spectra characteristics of c‐type cytochromes. The 15 kDa cytochrome shows two n = 1 components in potentiometric redox titrations with midpoint potentials at −130 and −270 mV in the membrane; both were slightly lower in detergent‐solubilized preparations. We suggest a designation of cytochrome cc m for this species. Its properties suggest a function as a transmembrane electron carrier between hydrogen and sulfate.

Comparative effectiveness of antifouling treatment regimes using chlorine or a slow-releasing bromine biocide☆

Abstract Five chlorine (Cl 2 ) and three slow-releasing bromine biocide [1-bromo-3-chloro-5,5-dimethylhydantoin (BCDMH)] treatment regimes were compared under laboratory conditions to determine their effectiveness in controlling the fouling of 304L stainless steel heat exchanger tubing. The most effective Cl 2 treatments were low level (0.1 ppm or less) continuous applications. Three intermittent Cl 2 treatments (1 h day −1 at 1.0 ppm, 1 h day −1 at 0.5 ppm, and 3 × 20 min day −1 at 0.5 ppm) were about equally effective. However, all three intermittent regimes were significantly less effective than the low level continuous treatments. The effectiveness of BCDMH treatment was similar to Cl 2 when used intermittently at similar residual concentrations as Cl 2 for 1 h day −1 and continuously at low levels. These experiments indicated that low level continuous treatment was more effective than intermittent treatment for controlling biofouling.

Pathways of Electron Transfer in Desulfovibrio

Sulfate reducing, bacteria of the genus Desulfovibrio conduct anaerobic respiration, conserving energy through oxidative phosphorylation in anaerobic sulfate reduction (1,2). The reduction of sulfate is mediated by an electron transport system composed of dehydrogenases, electron carriers, and a series of reductases (3,5). Some of the enzymes and electron carries involved are found exclusively in the membrane fraction although a great many are soluble.