Microbial-mediated removal of acrylamide from canal systems

Acrylamide (AMD), a neurotoxin and suspected carcinogen, is present up to 0.05% in linear anionic polyacrylamide (PAM) which is being evaluated as a canal sealant across the western United States. The capacity of canal microorganisms to facilitate AMD degradation was examined to constrain risks of PAM applications. AMD degradation under simulated groundwater flow was determined with soil column tests (repacked and soil cores) and spiked bottle tests verified microbial degradation under in situ and ex situ conditions. Results of the repacked columns indicate AMD degradation in the presence of competing substrates with half-lives ranging from 0.9 to 3.12 hours. Soil core column tests, with AMD half-lives of ∼34.1 hours and removal of spiked AMD (up to 5 ppm) within 12 days confirmed ability of AMD degradation by natural populations of microorganisms. Phylogenetic analysis of an AMD-degrading isolate collection concluded close sequence similarity to characterized, common bacteria belonging to several phyla

Geomicrobiological Changes in Two Ephemeral Desert Playa Lakes in the Western United States

The geochemistry and microbiology of two ephemeral playa lakes in the Western United States, Surprise Valley Alkali Lake (SVAL) and Eldorado Playa (EP), were examined over one wetting cycle, revealing dramatic temporal changes in suspended mineralogy, aqueous chemistry, and bacterial populations. In SVAL the predominant suspended mineral changed from smectite to vermiculite and clinoptilolite, which led to a depletion of soluble Mg2+. Nitrate became depleted in both playas as a result of biological nitrogen demand imparted by unusually dense microbial communities reaching 1 × 108 cultivable heterotrophs per ml of water. One hundred eighty eight bacterial isolates were obtained, representing sixty phylotypes and four phyla: Actinobacteria, Bacteroidetes, Proteobacteria, and Firmicutes. Phylogenetic analyses suggested that the microbial communities reflected different phases of succession, with SVAL changing from a diverse community with abundant Yonghaparkia to a less diverse late summer community with abundant Bacteroidetes and Proteobacteria such as Loktanella, Rhodobaca, Saccharospirillum, Flexibacter, and phylogenetically novel members of the Flexibacteriaceae. In EP, a diverse assemblage of bacteria often associated with soils was replaced very quickly by a much less even community dominated by Yonghaparkia, Sandarakinorhabdus, and relatives of Belliella baltica. Strikingly, the early summer microbial community from SVAL was not significantly different from the EP community that developed within one week of flooding, even though these playas are almost 1000 km apart, whereas sympatric communities in different phases of succession were different. To our knowledge, this is one of the first geomicrobiological studies of a recharge playa, the dominant playa type worldwide

VirB Alleviates H-NS Repression of the icsP Promoter in Shigella flexneri from Sites More Than One Kilobase Upstream of the Transcription Start Site▿

The icsP promoter of Shigella spp. is repressed by H-NS and derepressed by VirB. Here, we show that an inverted repeat located between positions −1144 and −1130 relative to the icsP transcription start site is necessary for VirB-dependent derepression. The atypical location of this cis-acting site is discussed