The abundance and distribution of microorganisms and their potential for mineralizing polycyclic aromatic hydrocarbons (PAHs) were measured in subsurface sediment samples at two geographically separate buried coal-tar sites. At a relatively undisturbed forested site in the northeastern United States, metabolic adaptation to the PAHs was evident: Radiolabeled naphthalene and phenanthrene were converted to (14)CO2 in core material from inside but not outside a plume of groundwater contamination. However, at the urban site in the midwestern United States these PAHs were mineralized in sediments from both contaminated and uncontaminated boreholes. Thus, clear qualitative evidence showing an adaptational response by the subsurface microbial community was not obtained at the urban site. Instead, subtler clues suggesting metabolic adaptation by subsurface microorganisms from the urban site were discerned by comparing lag periods and extents of (14)CO2 production from radiolabeled PAHs added to samples from contaminated and uncontaminated boreholes. Despite slightly higher PAH mineralization activity in contaminated borehole samples, p-hydroxybenzoate was mineralized equally in all samples from the urban site regardless of location. No striking trends in the abundances of actinomycetes, fungi, and either viable or total bacteria were encountered. However, colonies of the soil bacterium, Bacillus mycoides, were detected on enumeration plates of several samples from unsaturated and saturated zones in both urban boreholes. Furthermore, other common soil bacteria, Myxococcus xanthus and Chromobacterium violaceum, were identified in samples from the uncontaminated urban borehole. The occurrence of bacteria usually restricted to surface soil, combined with the observation of fragments of building materials in many of the core samples, suggested that past excavation and backfilling operations may have caused mixing of surface soil with subsurface materials at the urban site. We speculate that this mixing, as well as non-coal-tar-derived sources of PAHs, contributed to the PAH-mineralizing activity present in the sediment samples from the uncontaminated urban borehole.

Field experiments utilizing randomized block designs were implemented to assess the mobility of both coal tar-derived aromatic hydrocarbons and bacteria capable of metabolizing these substances at a contaminated field site. Arrays of sorbent materials wrapped in fiberglass mesh fabric were inserted into organic matter-rich freshwater sediments in order to intercept mobile chemicals and bacteria carried by the prevailing hydraulic gradient. Polyurethane foam plugs served as a sorbent for aqueous-phase coal tar components while sterile sand from the site served as a substrate for colonization by bacteria. Replicate sorbents were removed from the sediments at varying intervals and assessed for organic compounds (via gas chromatography/mass spectrometry) and for numbers of aromatic hydrocarbon-degrading bacteria (via viable plate counts). Organic contaminants including naphthalene, methyl naphthalene, indenes, and substituted benzenes were detected in the foam sorbents. Contaminant concentrations reached a maximum after 15 days before diminishing. Both naphthalene-and phenanthrene-utilizing bacteria were mobile and reached peak titers of 10 4 and 10 3.3 , respectively, within 11 days. Thus, comigration of both contaminants and microorganisms occurred at the study site. Furthermore, the in situ abundances of contaminants and microorganisms reflect a dynamic balance between processes causing accrual and elimination.

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Six tributary streams and southern Cayuga Lake in central New York state were sampled for the presence ofSalmonella on swabs immersed for 4 days. Of a total of 322 swabs, 39% yielded salmonellae. Swabs were cultured in tetrathionate enrichment at 41.5°C. Isolations were made from brilliant green agar. Salmonellae were isolated from many sites on the streams and from some lake sites. Twenty-five serotypes (11 somatic antigen groups) and a distinct biotype of S. typhimurium (H2S negative) were found. Most frequent isolates, in order of decreasing occurrence, were S. typhimurium, S. thompson, S. oranienburg, and S. enteritidis. Several uncommon isolates also appeared. When tested for mouse infectivity, the isolates generally showed little or no virulence. The incidence of clinical salmonellosis among humans was low in the area and the variety of serotypes had not been noted among cattle. The presence of Salmonella in waters ranging in classification from potable to agricultural and industrial indicated the existence of a low level and undefined reservoirs of the bacteria in the region.

The heat-resistant Salmonella senftenberg 775W and two strains of Staphylococcus aureus were tested at temperatures up to 68.3 C (71.1 C for S. senftenberg) in four different media. From the survival data, decimal reduction times (D values) were calculated for each set of conditions, and decimal reduction time curves were constructed for each bacterial strain in each medium. Slopes of decimal reduction time curves (ZD) ranged from 4.52 to 6.38 C with a single exception. There was no statistical heterogeneity among the remaining values. Results were in close agreement with published results of similar studies conducted at somewhat lower temperatures and support the practice of using a slope value (ZD) of 5.56 C for establishing time-temperature relationships for food processing. It is recommended that such a decimal reduction time curve not be extrapolated to temperatures more than 5.56 C higher than those actually tested. Modern technology has made available many new food products, frozen, canned, or dried, both cooked and uncooked. The wide distribution of many of these products, with their increasing use for quantity service in cafeterias and large