Search

This study examined the microbial community in an acidic stream draining across the Yun-Fu pyrite mine (Guangdong, China), where extremely acidic mine water is a persistent feature due to the intensive surface mining activities. Analysis of terminal restriction fragment length polymorphism (TRFLP) of 16S rRNA gene sequences showed that microbial populations varied spatially and seasonally and correlated with geochemical and physical conditions. After the stream moves from underground to the surface, the microbial community in the acidic water rapidly evolves into a distinct community close to that in the downstream storage pond. Comparisons of TRFLP peaks with sequenced clone libraries indicated that bacteria related to the recently isolated iron-oxidizer Ferrovum myxofaciens dominated the acidophilic community throughout the year except for the samples collected in spring from the storage pond, where Ferroplasma acidiphilum-like archaea represented the most abundant group. Acidithiobacillus ferrooxidans-affiliated organisms increased along the acid stream and remained common over the year, whereas Leptospirillum ferrooxidans-like bacteria were negligible or even not detected in the analyzed samples. The data indicate that changes in environmental conditions are accompanied by significant shifts in community structure of the prokaryotic assemblages at this opencast mining site.

Cultivation-based and molecular approaches were used to characterize the phylogenetic composition and structure of the microbial community in an extremely acidic (pH 2.0) acid mine drainage (AMD) associated with Pb/Zn mine tailings that were undergoing vigorous acid generation. Acidophilic bacteria were isolated and enumerated on solid media, and were found to be restricted to isolates related to Acidithiobacillus ferrooxidans and Acidiphilium cryptum. By contrast, cloning and phylogenetic analysis of 16S rRNA genes revealed that, although low in total taxonomically distinct groups, the tailings AMD ecosystem harbored a wide range of phylogenetically diverse microbes. Of the 141 clones examined, 104 were phylogenetically affiliated with the recently discovered, iron-oxidizing Leptospirillum group III within the Nitrospira. It thus appears that iron serves as the major electron donor in this habitat. Thirty clones were affiliated with the Proteobacteria, half of which belonged to organisms related to Alphaproteobacteria species capable of ferric iron reduction. Other clones were grouped with Betaproteobacteria and Gammaproteobacteria (six clones each), and even with Deltaproteobacteria (three clones), a subdivision with anaerobic sulfate or metal (iron) reduction as the predominant physiological trait of its members. Finally, four clones were clustered within the Firmicutes and the Acidobacteria. Approximately half of the sequence types representing the majority of the total clones fell into lineages that are poorly represented by cultured organisms or have thus far been represented by only a few environmental sequences. Thus, the present study extends our knowledge of the biodiversity of microorganisms populating highly acidic AMD environments.

A study was conducted to compare three automated systems and the Gram stain for their ability to detect significant bacteriuria. A total of 1,000 urine specimens were evaluated by Autobac MTS (General Diagnostics), Auto Microbic system (AMS; Vitek Systems, Inc.), and MS-2 (Abbott Laboratories) and compared with a semiquantitative culture plate method. Two hundred thirty-nine (23.9%) specimens had colony counts of >10(5) colony-forming units (CFU)/ml by the culture plate method (group I). Of these, 204 (85.3%) were positive by Autobac, 198 (82.8%) were positive by AMS, and 179 (74.9%) were positive by MS-2. When pure cultures of diphtheroids, lactobacilli, and viridans streptococci not group D were considered contaminants and therefore excluded, there were 118 specimens containing pure cultures of probable pathogens. The percentage of significant isolates detected was 97.4% (115 of 118) by the Gram stain, 96.6% (114 of 118) by Autobac, and 95.8% (113 of 118) by AMS and MS-2. The average detection time for all organisms was 2.2 h by Autobac, 6.1 h by AMS, and 1.8 h by MS-2; therefore, all three methods were more rapid than the 18- to 24-h standard plate culture method. One hundred sixty-one (16.1%) specimens had colony counts of 10(4) to 10(5) CFU/ml (group II). The probable pathogens not detected in this group were two (1.2%) by Autobac and MS-2 and three by AMS (1.9%). The average detection time for group II was 4.2 h by Autobac, 8.9 h by AMS, and 3.8 h by MS-2. Six hundred specimens had colony counts of <10(4) CFU/ml. Of these, 188 had colony counts equal to 10(3) and <10(4) CFU/ml (group III), and 412 cultures were below detectable limits by the standard plate method (group IV). Less than 37 and 15% of groups III and IV, respectively, were detected by instrumentation. Average detection times for groups III and IV were 4.6 and 4.8 h by Autobac, 10 and 11 h by AMS, and 4.2 and 4.4 h by MS-2. The cost of supplies and technical time with Gram stain, Autobac, and MS-2, when used as screening methods, were comparable and considerably less expensive than for the reference method. The AMS was the least expensive system when the cost for identifying probable pathogens was included.