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The dynamic interaction of bacteria within bed sediment and suspended sediment (i.e., floc) in a wave-dominated beach environment was assessed using a laboratory wave flume. The influence of shear stress (wave energy) on bacterial concentrations and on the partitioning and transport of unattached and floc-associated bacteria was investigated. The study showed that increasing wave energy (0.60 and 5.35 N/s) resulted in a 0.5 to 1.5 log increase in unattached cells of the test bacterium Pseudomonas sp. strain CTO7::gfp-2 in the water column. There was a positive correlation between the bacterial concentrations in water and the total suspended solids, with the latter increasing from values of near 0 to up to 200 mg/L over the same wave energy increase. The median equivalent spherical diameter of flocs in suspension also increased by an order of magnitude in all experimental trials. Under both low (0.60 N/s) and high (5.35 N/s) energy regime, bacteria were shown to preferentially associate with flocs upon cessation of wave activity. The results suggest that collecting water samples during periods of low wave action for the purpose of monitoring the microbiological quality of water may underestimate bacterial concentrations partly because of an inability to account for the effect of shear stress on the erosion and mobilization of bacteria from bed sediment to the water column. This highlights the need to develop a more comprehensive beach analysis strategy that not only addresses presently uncharacterized shores and sediments but also recognizes the importance of eroded flocs as a vector for the transport of bacteria in aquatic environments.

An anaerobic microbial consortium able to biodegrade saturation levels of perchloroethylene (PCE) in a column containing a source zone of PCE was examined phylogenetically to determine microbial community structure and spatial variation in relation to the PCE source. The consortium was comprised of at least 34 members with 7 organisms sharing affiliations with known respiratory or cometabolic dechlorinators. Seven other organisms had their closest phylogenetic relative detected in other environments containing chlorinated compounds. Based on denaturing gradient gel electrophoresis, significant Bacteria were Dehalococcoides ethenogenes, Shewanella putrefaciens, and an Acetobacterium species. Spatial variations in community structure of the consortium relative to the PCE source zone were observed. A Pseudomonas species was predominant in a zone 30 cm from the PCE source. A Methanothrix species was predominant at points over 85 cm from the source zone. A Trichlorobacter species was detected where PCE concentrations were highest, up to 85 cm from the PCE source, whereas D. ethenogenes was ubiquitous to over 128 cm from the PCE source.

Resin acids, a group of diterpenoid carboxylic acids present mainly in softwood species, are present in many pulp mill effluents and toxic to fish in recipient waters. They are considered to be readily biodegradable. However, their removal across biological treatment systems has been shown to vary. Recent studies indicate that natural resin acids and transformation products may accumulate in sediments and pose acute and chronic toxicity to fish. Several resin acid biotransformation compounds have also been shown to bioaccumulate and to be more resistant to biodegradation than the original material. Until recently, the microbiology of resin-acid degradation has received only scant attention. Although wood-inhabiting fungi have been shown to decrease the level of resin present in wood, there is no conclusive evidence that fungi can completely degrade these compounds. In contrast, a number of bacterial isolates have recently been described which are able to utilize dehydroabietic or isopimaric acids as their sole carbon source. There appears to be an unusually high degree of substrate specificity with respect of the utilization of abietane congeners and the presence of substituents. Pimaranes do not appear to be attacked to the same extent as the abietanes. This paper reviews the occurrence, chemistry, toxicity, and biodegradation of resin acids in relation to the biological treatment of pulp and paper mill effluents.

Water samples from the wastewater treatment system of a bleach kraft mill and from the river that supplies the mill were plated on six different media and culturable isolates were screened for substrate utilization patterns, taxonomic characters, plasmid content, and resistance to ampicillin, streptomycin, kanamycin, tetracycline, naldixic acid, mercury, nickel, copper, cobalt, cadmium, and zinc. A cluster analysis of the substrate utilization profiles and taxonomic characters revealed that Pseudomonas, Acinetobacter, and Acidovorax spp. were common among the culturable isolates from the river, while Ancylobacter aquaticus, Klebsiella spp., and an unknown group of pleomorphic Gram-negative methylotrophs were common among the culturable isolates from the mill treatment system. Of isolates from the settling pond and aerated lagoon, 78 and 64% carried plasmids, while only 56% of isolates from the river carried plasmids. Plasmids were significantly associated with resistance to cadmium but not with any other resistance characters. Large numbers of plasmid-carrying A. aquaticus strains and pleomorphic methylotrophs accounted for high plasmid incidence levels in the mill treatment system, and the ability to dechlorinate simple aliphatic substrates was found in these two groups as well as in one Pseudomonas strain.

Potential toxicity of 2-aminophenoxazin-3-one to 20 bacterial species and two fungi and its inactivation under anaerobic conditions were investigated. Minimum inhibitory concentration for cellulolytic bacteria was in the range of 50-100 micrograms.mL-1, but at 100 micrograms.mL-1 of 2-aminophenoxazin-3-one, there was no effect on the growth of any of the noncellulolytic bacteria. Four noncellulolytic bacterial strains showed no inhibition of growth, even at 200 micrograms.mL-1 of this compound. Under anaerobic conditions and in the presence of cysteine, the long wavelength absorption band of this compound slowly shifted from about 434 to 320 nm, and its inhibitory effect on RNA synthesis was relieved after one-half of a generation time in cultures of cellulolytic ruminal bacteria. A similar shift of absorption band was observed in rumen fluid filtered through a 0.22-microns Millipore filter. It was concluded that protonation of 2-aminophenoxazin-3-one under anaerobic conditions present in the rumen would considerably reduce its potential toxicity to cellulolytic bacteria.

A metabolite of Trichoderma hamatum, 3-(3-isocyanocyclopent-2-enylidene)propionic acid, was tested for its effects on growth of and carbohydrate metabolism in 11 strains of functionally important rumen bacteria. To standardize the biological activity of this unstable metabolite, a rapid, aerobic disc diffusion assay was developed using Escherichia coli ATCC 11775. In an anaerobic broth dilution assay using a medium lacking rumen fluid and containing a soluble carbohydrate, the minimum inhibitory concentration of the metabolite which completely inhibited growth of the rumen bacteria for 18 h at 39 degrees C was generally less than 10 micrograms X mL-1; however, the minimum inhibitory concentrations for Megasphaera elsdenii B159 and Streptococcus bovis Pe(1)8 were 10-25 and 25-64 micrograms X mL-1, respectively. In general, the Gram-negative strains were more sensitive than the Gram positive. The minimum inhibitory concentration for Bacteroides ruminicola 23 grown with glucose was 1 micrograms X mL-1; for B. ruminicola GA33 (glucose), B. succinogenes S85 (cellobiose), and Succinivibrio dextrinosolvens 24 (maltose), it was 2 microgram X mL-1. When added to a cellulose-containing rumen fluid medium, 1-4 micrograms X mL-1 of the metabolite delayed cellulose hydrolysis by B. succinogenes S85, Ruminococcus albus 7, and R. flavefaciens FD1 for up to 4 days, and 6-7 micrograms X mL-1 prevented hydrolysis for at least 1 month. In the presence of the metabolite, the proportion of acetate produced from soluble carbohydrate by the majority of strains increased, but with some strains net production of acetate decreased relative to production of other acidic fermentation products.(ABSTRACT TRUNCATED AT 250 WORDS)