No abstract

Biodegradation of phenanthrene, biphenyl, or di(2 ethylhexyl) phthalate initially present in a variety of nonaqueous phase liquids (NAPLs) was slow in samples of soil and aquifer solids The NAPLs were hexadecane, dibutyl phthalate, 2,2,4,4, 6,8,8-heptamethylnonane, cyclohexane, commercial oils, crude oil, creosote, and kerosene Slurrying the soil or aquifer solids markedly enhanced the rate and extent of mineralization of the test compounds initially in many of the NAPLs Both the low rate and the extent of mineralization of the three compounds initially in dibutyl phthalate in soil slurries and of di(2 ethylhexyl) phthalate in heptamethylnonane present in slurries of aquifer solids were increased by inoculation of acclimated microbial cultures Increasing the NAPL volume decreased phenanthrene biodegradation in soil, but the effect of larger NAPL volume could be alleviated by slurrying and inoculation The rate or extent of mineralization in aquifer slurries of di(2-ethylhexyl) phthalate initially in some NAPLs was increased by addition of N and P, and inoculation further enhanced the degradation

Ascaris suum eggs were inactivated in distilled water and digested sludge by butanoic, pentanoic, and hexanoic acids. The fatty acids (short-chain fatty acids [SCFA]) were effective only when protonated and at sufficient concentrations. The conjugate bases were not effective at the concentrations evaluated. Predictions from an inhibition model (50% inhibitory concentration [IC 50 ]) based on quantitative structure-activity relationships were congruent with inactivation data.The nematode Ascaris lumbricoides releases highly resistant, unembryonated eggs into the environment, causing ϳ1.3 billion illnesses worldwide (12). The swine parasite Ascaris suum is routinely used as a surrogate for the human parasite (22) and is often found in sludges. Due to its resistance to biocontrol mechanisms (6) Ascaris is a model organism for developing environmentally safe disinfection methods (7,22). The eggs can be rendered nonviable through natural processes using extreme heat (Ͼ40°C) or with UV radiation (4). The use of short-chain fatty acids (SCFA) is another possible method of controlling Ascaris. The toxicity of SCFA to bacteria, e.g., Escherichia coli (9), Streptococcus, and Staphylococcus (20), fungi (14, 23), insects (15), and birds (13) a Letters after viability measurements denote statistically significant differences among the percentages of viable eggs when compared to the water controls which were conducted with each round of testing (data not shown). The overall average percent survival for the water controls was 90.3 Ϯ 2.7%. Data marked "a" were tested with the Proc Mix of SAS (P Ͻ 0.01). Data marked "b" were tested with the Student t test (P Ͻ 0.05). SD, standard deviation.b ND, not done.

Microelectrophoresis is a common technique for probing the surface chemistry of the Cryptosporidium parvum oocyst. Results of previous studies of the electrophoretic mobility of C. parvum oocysts in which microelectrophoresis was used are incongruent. In this work we demonstrated that capillary electrophoresis may also be used to probe the surface characteristics of C. parvum oocysts, and we related the surface chemistry of C. parvum oocysts to their stability in water. Capillary electrophoresis results indicated that oocysts which were washed in a phosphate buffer solution had neutrally charged surfaces. Inactivation of oocysts with formalin did not influence their electrophoretic mobility, while oocyst populations that were washed in distilled water consisted of cells with both neutral and negative surface charges. These results indicate that washing oocysts in low-ionic-strength distilled water can impart a negative charge to a fraction of the oocysts in the sample. Rapid coagulation experiments indicated that oocysts did not aggregate in a 0.5 M NaCl solution; oocyst stability in the salt solution may have been the result of Lewis acid-base forces, steric stabilization, or some other factor. The presence of sucrose and Percoll could not be readily identified on the surface of C. parvum oocysts by attenuated total reflectance-Fourier transform infrared spectroscopy, suggesting that these purification reagents may not be responsible for the stability of the uncharged oocysts. These findings imply that precipitate enmeshment may be the optimal mechanism of coagulation for removal of oocysts in water treatment systems. The results of this work may help elucidate the causes of variation in oocyst surface characteristics, may ultimately lead to improved removal efficiencies in full-scale water treatment systems, and may improve fate and transport predictions for oocysts in natural systems.

Dissolved chemical inducers of settlement behavior of veliger larvae of the oysterCrassostrea gigas are found in supernatants of both pigmented species of bacteria (Alteromonas colwelliana, Vibrio cholerae strain HTX) as well as nonpigmented bacteria (Excherichia coli, Vibrio cholerae strain 596-B). Usually less than 10% of veligers exhibited settlement behavior in response to supernatants from the early bacterial growth phases, whereas 30-90% of larvae responded when exposed to supernatant from late-log and stationary phase cultures. Percentages of larvae exhibiting settlement behavior were inversely correlated with oxygen levels in the culture. Furthermore, the behavioral response decreased with pigment formation, suggesting that quantities of noxious compounds such as quinones may build up in the supernatants of cultures of pigmented bacteria. Tyrosinase, an enzyme that converts L-tyrosine to L-DOPA in the first step of melanogenesis, was detected both in the bacterial pellet and the supernatant during growth of the pigmented species. The enzyme is not required for the production of settlement inducer as the nonpigmented speciesE. coli andV. cholerae (596-B) also released inducer into the supernatant and had no detectable tyrosinase. The data suggest either that there is more than one inducer of settlement behavior found in bacterial supernatants or that the inducer is not L-DOPA or an L-DOPA-mimetic associated with the melanin biochemical pathway.