Search

Aphanizomenon flos-aquae (AFA) is the dominant filamentous cyanobacterium that develops into blooms in Upper Klamath Lake, Oregon, each year. During AFA bloom and collapse, ecosystem conditions for endangered Lost River and shortnose suckers deteriorate, thus motivating the need to identify processes that limit AFA abundance and decline. Here, we investigate the relations between AFA and other members of the microbial community (photosynthetic and nonphotosynthetic bacteria and archaea), how those relations impact abundance and collapse of AFA, and the types of microbial conditions that suppress AFA. We found significant spatial variation in AFA relative abundance during the 2016 bloom period using 16S rRNA sequencing. The Pelican Marina site had the lowest AFA relative abundance, and this was coincident with increased relative abundance of Candidatus Sericytochromatia, Flavobacterium , and Rheinheimera , some of which are known AFA antagonists. The AFA collapse coincided with phosphorus limitation relative to nitrogen and the increased relative abundance of Cyanobium and Candidatus Sericytochromatia, which outcompete AFA when dissolved inorganic nitrogen is available. The data collected in this study indicate the importance of dissolved inorganic nitrogen combined with microbial community structure in suppressing AFA abundance. [ABSTRACT FROM AUTHOR]

The efficiency of contaminant biodegradation in ground water depends, in part, on the transport properties of the degrading bacteria. Few data exist concerning the transport of bacteria in saturated bedrock, particularly at the field scale. Bacteria and microsphere tracer experiments were conducted in a fractured crystalline bedrock under forced-gradient conditions over a distance of 36 m. Bacteria isolated from the local ground water were chosen on the basis of physicochemical and physiological differences (shape, cell-wall type, motility), and were differentially stained so that their transport behavior could be compared. No two bacterial strains transported in an identical manner, and microspheres produced distinctly different breakthrough curves than bacteria. Although there was insufficient control in this field experiment to completely separate the effects of bacteria shape, reaction to Gram staining, cell size, and motility on transport efficiency, it was observed that (1) the nonmotile, mutant strain exhibited better fractional recovery than the motile parent strain; (2) Gram-negative rod-shaped bacteria exhibited higher fractional recovery relative to the Gram-positive rod-shaped strain of similar size; and (3) coccoidal (spherical-shaped) bacteria transported better than all but one strain of the rod-shaped bacteria. The field experiment must be interpreted in the context of the specific bacterial strains and ground water environment in which they were conducted, but experimental results suggest that minor differences in the physical properties of bacteria can lead to major differences in transport behavior at the field scale., Introduction Bioaugmentation, which involves amendments of genetically engineered or specialized bacteria to contaminated subsurface environments for purposes of enhancing biodegradation, is becoming a potential alternative to conventional pump-and-treat technologies. Although [...]

Research has been conducted on the porous-medium-grown Spumella guttula transport and attachment behavior. The effect of the staining procedure on the adjective transport investigated via comparison of the live and dead S. guttula and the results of its pH-dependent attachment behavior are reported.

A study of viral transport in sewage-contaminated and uncontaminated portions of an aquifer showed the effects of organic matter concentration and aquifer grain surface properties on viral attachment to aquifer grains. The presence of organic matter decreased viral transport through the aquifer, accounting for an 83% attenuation of viral particles, while in the uncontaminated portion of the aquifer, attenuation of viral particles was only at 42%. Monitoring of viral transport was done by radiolabeling of bacteriophage.

The buoyant densities of groundwater bacteria and microflagellates (protozoa) may provide insights into understanding a microorganism's rate of immobilization, retardation, and sedimentation within sandy aquifer sediments. Observations on microorganisms found in sandy aquifers using the density-gradient centrifugation and Stoke's law approximation methods show that sedimentation is important in predicting subsurface transport of less buoyant cultured bacteria, but negligible in predicting those of the more buoyant free living bacteria.

1. Introduction Virus transport in sandy aquifer material has been observed to follow that of soluble salts in that virus are subject to dispersion in flowing ground water, and under [...]

Examination of the transport behavior of groundwater flagellated protozoa and flagellate-sized carboxylated microspheres in sandy, organically polluted aquifer sediments using small-scale tracer tests reveals that the 2-micrometer flagellates have the optimum size for transport. Presence of aquifer sediments induces significant flagellate immobilization. Experimental data reveal the decrease in the immobilization rates of laboratory-grown flagellates with increasing time and distance of travel.

The metabolic status of microbial communities in a contaminated plume at Cape Cod was studied using nucleic acid and adenylate indicators, which included adenylate energy charge, total adenine nucleotides, DNA levels and ATP to DNA ratios. The results showed that these indicators may be useful tools in assessing the metabolic status of free-living bacteria in contaminated aquifers. However, since the bacterial DNA content may change in response to nutrient conditions, care should be taken in using the ATP/DNA ratio in such studies.

The way in which the sorption of groundwater bacteria through a contaminated sandy aquifer was affected by sediment surface and pH was studied. The study also investigated the way in which sorption was affected by the composition of water, organic matter in water and coatings of oxyhydroxide on grains of sand. The results indicated that the sorption and desorption of bacteria through aquifer sediments were greatly affected by the geochemistry of the groundwater.