Geology topics

Jodi Switzer Blum

Publications and source records attributed to Jodi Switzer Blum.

4 recordsLinked to original sources

USGS2012

Desulfohalophilus alkaliarsenatis gen. nov., sp. nov., an extremely halophilic sulfate- and arsenate-respiring bacterium from Searles Lake, California

A haloalkaliphilic sulfate-respiring bacterium, strain SLSR-1, was isolated from a lactate-fed stable enrichment culture originally obtained from the extreme environment of Searles Lake, California. The isolate proved capable of growth via sulfate-reduction over a broad range of salinities (125–330 g/L), although growth was slowest at salt-saturation. Strain SLSR-1 was also capable of growth via dissimilatory arsenate-reduction and displayed an even broader range of salinity tolerance (50–330 g/L) when grown under these conditions. Strain SLSR-1 could also grow via dissimilatory nitrate reduction to ammonia. Growth experiments in the presence of high borate concentrations indicated a greater sensitivity of sulfate-reduction than arsenate-respiration to this naturally abundant anion in Searles Lake. Strain SLSR-1 contained genes involved in both sulfate-reduction ( dsrAB ) and arsenate respiration ( arrA ). Amplicons of 16S rRNA gene sequences obtained from DNA extracted from Searles Lake sediment revealed the presence of close relatives of strain SLSR-1 as part of the flora of this ecosystem despite the fact that sulfate-reduction activity could not be detected in situ. We conclude that strain SLSR-1 can only achieve growth via arsenate-reduction under the current chemical conditions prevalent at Searles Lake. Strain SLSR-1 is a deltaproteobacterium in the family Desulfohalobiacea of anaerobic, haloalkaliphilic bacteria, for which we propose the name Desulfohalophilus alkaliarsenatis gen. nov., sp. nov.

California↗

USGS2011

Response to comments on "A bacterium that can grow using arsenic instead of phosphorus"

Concerns have been raised about our recent study suggesting that arsenic (As) substitutes for phosphorus in major biomolecules of a bacterium that tolerates extreme As concentrations. We welcome the opportunity to better explain our methods and results and to consider alternative interpretations. We maintain that our interpretation of As substitution, based on multiple congruent lines of evidence, is viable.

Science↗

USGS2007

Alkalilimnicola ehrlichii sp. nov., a novel, arsenite-oxidizing haloalkaliphilic gammaproteobacterium capable of chemoautotrophic or heterotrophic growth with nitrate or oxygen as the electron acceptor

A facultative chemoautotrophic bacterium, strain MLHE-1 T , was isolated from Mono Lake, an alkaline hypersaline soda lake in California, USA. Cells of strain MLHE-1 T were Gram-negative, short motile rods that grew with inorganic electron donors (arsenite, hydrogen, sulfide or thiosulfate) coupled with the reduction of nitrate to nitrite. No aerobic growth was attained with arsenite or sulfide, but hydrogen sustained both aerobic and anaerobic growth. No growth occurred when nitrite or nitrous oxide was substituted for nitrate. Heterotrophic growth was observed under aerobic and anaerobic (nitrate) conditions. Cells of strain MLHE-1 T could oxidize but not grow on CO, while CH 4 neither supported growth nor was it oxidized. When grown chemoautotrophically, strain MLHE-1 T assimilated inorganic carbon via the Calvin–Benson–Bassham reductive pentose phosphate pathway, with the activity of ribulose 1,5-bisphosphate carboxylase (RuBisCO) functioning optimally at 0.1 M NaCl and at pH 7.3. Strain MLHE-1 T grew over broad ranges of pH (7.3–10.0; optimum, 9.3), salinity (15–190 g l −1 ; optimum 30 g l −1 ) and temperature (13–40 °C; optimum, 30 °C). Phylogenetic analysis of 16S rRNA gene sequences placed strain MLHE-1 T in the class Gammaproteobacteria (family Ectothiorhodospiraceae ) and most closely related to Alkalispirillum mobile (98.5 %) and Alkalilimnicola halodurans (98.6 %), although none of these three haloalkaliphilic micro-organisms were capable of photoautotrophic growth and only strain MLHE-1 T was able to oxidize As(III). On the basis of physiological characteristics and DNA–DNA hybridization data, it is suggested that strain MLHE-1 T represents a novel species within the genus Alkalilimnicola for which the name Alkalilimnicola ehrlichii is proposed. The type strain is MLHE-1 T (=DSM 17681 T =ATCC BAA-1101 T ). Aspects of the annotated full genome of Alkalilimnicola ehrlichii are discussed in the light of its physiology.

California↗

USGS1992

Nitrate is a preferred electron acceptor for growth of freshwater selenate-respiring bacteria

An anaerobic, freshwater enrichment grew with either nitrate or selenate as an electron acceptor. With both ions present, nitrate reduction preceded selenate reduction. An isolate from the enrichment grew on either ion, but the presence of nitrate precluded the reduction of selenate. Stock cultures of denitrifiers grew anaerobically on nitrate but not on selenate.

Applied and Environmental Microbiology↗