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The microbial communities in solar salterns and a soda lake have been characterized using two techniques: BIOLOG, to estimate the metabolic potential, and amplicon length heterogeneity analysis, to estimate the molecular diversity of these communities. Both techniques demonstrated that the halophilic Bacteria and halophilic Archaea populations in the Eilat, Israel saltern are dynamic communities with extensive metabolic potentials and changing community structures. Halophilic Bacteria were detected in Mono Lake and the lower salinity ponds at the Shark Bay saltern in Western Australia, except when the crystallizer samples were stressed by exposure to Acid Green Dye #9899. At Shark Bay, halophilic Archaea were found only in the crystallizer samples. These data confirm both the metabolic diversity and the phylogenetic complexity of the microbial communities and assert the need to develop more versatile media for the cultivation of the diversity of bacteria in hypersaline environments.

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The whole community pigments and lipids have been examined during a 5-year period in two commercial solar salterns located in the United States and in Israel. There were significant differences in the complexity of the lipid and pigment patterns within the California saltern system, and these differences were not consistent over the sampling period despite examination of ponds with the same salinity. The solar saltern system in Eilat, Israel, showed greater consistency during this sampling period and compared directly with previous studies. The complexity of the saltern in Newark, California, could be explained on the basis of the prevailing weather conditions (cooler and more rainfall) and the nutrient-enriched source water. The Eilat saltern, however, has an oligotrophic water source and has a considerably warmer and drier climate. This difference resulted in more diverse and more complex pigment and lipid patterns and presumably microbial populations in the Newark, California, plant than in the saltern in Eilat, Israel.

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There are two groups of microorganisms that live and grow in hypersaline (>10-15% NaCl) environments: the halophilic Archaea and the halotolerant Bacteria and algae. In order to grow and reproduce in such high-salt, low-water activity environments, these organisms have made basic biochemical adaptations in their proteins, osmoregulation mechanisms, nucleic acids, and lipids. The environment of the halophiles and especially how the halophilic Archaea have adapted to that environment are reviewed in this paper. Along with this review is a brief description of how these adaptations could be important in the detection of life on early Mars assuming similar types of salts and a carbon-based life.

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Bacterial isolates were obtained from groundwater and soils contaminated with chlorobenzene (CB). The isolates were tested to determine whether the natural community could remove the groundwater contaminants. These isolates were identified and characterized as to their ability to grow on CB and related aromatic compounds. The complete consortium could mineralize approximately 54% of the CB within 7 days, with no accumulation of 3-chlorocatechol. Metabolic pathways were evaluated for several isolates. One phenotype was characterized by the ability to degrade CB by the modified ortho pathway. One strain also degraded p-dichlorobenzene by using the same pathway. Isolates exhibiting a second phenotype degraded p-cresol, benzene, and phenol by the classical ortho pathway and accumulated 3-chlorocatechol when grown in the presence of CB. Strains of the third phenotype grew on complex media in the presence of CB but did not transform any of the aromatic compounds tested. The results suggest that the indigenous microbial community at the contaminated site would be able to degrade CB if provided with the appropriate conditions.

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Sublethal levels (10 to 100 micrograms/ml) of the chlorinated insecticide chlordane (1,2,4,5,6,7,8,8-octachloro-3a,4,7,7a-tetrahydro-4,7-methanoindan) were introduced into the growth medium of the marine bacterium, Aeromonas proteolytica. Chlordane inhibited the synthesis of an extracellular endopeptidase by almost 40% but exhibited no such inhibition of the extracellular aminopeptidase also produced during the growth cycle. Studied with 14C-labeled chlordane demonstrated that the insecticide was not biologically degraded under the test conditions used and that up to 75% of the recoverable chlordane was cell associated within 48 h. Studied with uniformly labeled L[14C]valine and [2-14C]uracil established that neither the transport nor the incorporation of these protein and ribonucleic acid precursors was inhibited by chlordane. Separation of the membrane fractions using isopycnic centrifugation localized 14C-labeled chlordane in the cytoplasmic membrane. Also, chlordane inhibited the membrane-bound adenosine 5'-triphosphatase while the soluble (released) form of this enzyme remained unaffected. These data indicate that chlordane resides in the cytoplasmic membrane and may cause specific alterations in membrane-associated activities.

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A study was undertaken of the various factors affecting the recovery of heterotrophic bacteria from marine sediments. The dilution medium and culture medium were found to be of great importance in the recovery of heterotrophic colony forming units (CFU). Statistical analysis of the total viable counts obtained under the test conditions showed that artificial seawater (ASW) without further supplementation was equal to or superior to ASW plus 0.1% peptone or ASW plus 0.1% peptone and 0.1% glycerol. The addition of a surfactive agent, on the other hand, resulted in 95% inhibition of the recoverable CFU. The elapsed time (up to 12 hr) between recovery of a sedimentary core and completion of plating procedures was found to have little effect provided the sedimentary sample was removed from the core, placed in ASW, and stored in a refrigerator until actual plating occurred. It was further noted that lower organic nutrient concentrations, approximately one-tenth of those generally in use, resulted in significantly higher total viable counts. Finally, replicate contiguous sampling at three depths in a core resulted in no significant changes in the number of CFU from the surface samples, indicating a greater surface homogeneity than that previously suspected. The same pattern was not true, however, for samples obtained a lower positions in the core, thus indicating pockets of microbial concentration.

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Twenty-nine cultures isolated from nonaxenic growths of Chlorella sorokiniana (Shihira and Krauss) and eight reference cultures were tested for 150 morphological and biochemical characteristics. The taxonomic data were subjected to computer analysis from which five major clusters were identified. The bacterial isolates have been placed in the genera: Pseudomonas, Acinetobacter, Flavobacterium, and Bacillus. Amino acid requirements of four strains from the test set were determined.

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Biochemically deficient strains of Serratia marinorubra have been isolated with specific requirements for adenine, uracil, and threonine. Standard curves for dose to growth response have been obtained showing a linear sensitivity from 0.5 to 4.0 mg of adenine per liter of seawater, 0.1 to 2.0 mg of uracil per liter of seawater, and 0.5 to 10 mg of threonine per liter of seawater. These mutants have been used to test for the presence of their required metabolites in natural seawater samples from the Gulf of Mexico and adjacent bays. Of the three compounds under investigation, adenine was found in 10 samples, uracil in 2 samples, and threonine in none. The possible significance of these findings to the marine environment is discussed.

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