Fluctibacter corallii gen. nov., sp. nov., isolated from the coral Montipora capitata on a reef in Kane'ohe Bay, O'ahu, Hawai'i, reclassification of Aestuariibacter halophilus as Fluctibacter halophilus comb. nov., and Paraglaciecola oceanifecundans as a later heterotypic synonym of Paraglaciecola agarilytica.

Strain AA17T was isolated from an apparently healthy fragment of Montipora capitata coral from the reef surrounding Moku o Lo'e in Kane'ohe Bay, O'ahu, Hawai'i, USA, and was taxonomically evaluated using a polyphasic approach. Comparison of a partial 16S rRNA gene sequence found that strain AA17T shared the greatest similarity with Aestuariibacter halophilus JC2043T (96.6%), and phylogenies based on 16S rRNA gene sequences grouped strain AA17T with members of the Aliiglaciecola, Aestuariibacter, Lacimicrobium, Marisediminitalea, Planctobacterium, and Saliniradius genera. To more precisely infer the taxonomy of strain AA17T, a phylogenomic analysis was conducted and indicated that strain AA17T formed a monophyletic clade with A. halophilus JC2043T, divergent from Aestuariibacter salexigens JC2042T and other related genera. As a result of monophyly and multiple genomic metrics of genus demarcation, strain AA17T and A. halophilus JC2043T comprise a distinct genus for which the name Fluctibacter gen. nov. is proposed. Based on a polyphasic characterisation and identifying differences in genomic and taxonomic data, strain AA17T represents a novel species, for which the name Fluctibacter corallii sp. nov. is proposed. The type strain is AA17T (= LMG 32603 T = NCTC 14664T). This work also supports the reclassification of A. halophilus as Fluctibacter halophilus comb. nov., which is the type species of the Fluctibacter genus. Genomic analyses also support the reclassification of Paraglaciecola oceanifecundans as a later heterotypic synonym of Paraglaciecola agarilytica.

An Evaluation of the Quality of CPR Chest Compressions Performed on Football-Equipped and Obese Simulation Manikins.

OBJECTIVE: Protective athletic equipment may hamper the delivery of effective chest compressions. Unfortunately, an algorithm for managing cardiac arrest emergencies with equipment-laden athletes has yet to be established by national CPR certifying agencies. Further, athletes classified as being overweight or obese carry adipose in the thoracic region, which has been reported to inhibit the ability of rescuers to provide quality chest compressions. Thus, the purpose of this study was two-fold. The first purpose was to assess the ability of emergency responders to perform CPR chest compressions on an obese manikin. The second purpose was to analyze the effect of American football protective equipment on the performance of chest compressions by emergency responders. METHODS: Fifty emergency responders completed four 2-minute bouts of compression-only CPR. The scenarios included performing chest compressions on both traditional and obese CPR manikins, and performing chest compressions over a set of shoulder pads/chest protector that is used in the sport of American football on both traditional and obese manikins. RESULTS: The most notable outcomes in this study were related to chest compression depth, which fell well below the minimum recommended depth published by the American Heart Association in all conditions. Mean compression depth was significantly lower when performed on the obese manikin (avg over pads = 32.8, SD = 9.2 mm; avg no pads = 38.2, SD = 9.1 mm) compared to the traditional manikin (avg over pads = 40.0, SD = 10.9 mm; avg no pads = 40.8, SD = 14.8 mm), with statistical analyses revealing a significant effect due to both manikin size (p < 0.001) and the presence of equipment (p = 0.003), and a statistically significant interaction effect (p = 0.035). Chest recoil data revealed a statistically significant effect due to both manikin size (p = 0.017) and the presence of chest/shoulder safety pads (p = 0.003). CONCLUSION: Within this sample of emergency responders, chest compressions were adversely affected both by the equipment and obesity. Additionally, the traditional manikin received comparable chest compressions regardless of the presence or absence of football protective equipment, albeit both conditions resulted in poor depth performance.

Substantial Improvement in Self-Reported Mental Health Following Total Hip Arthroplasty Occurs Independent of Anesthetic Technique.

BACKGROUND: The influence of anesthetic type on mental health after total hip arthroplasty (THA) is poorly understood. Adverse effects of general anesthesia (GA) on cognition following major non-cardiac surgery are well known, but mental health following THA is less well-studied. We hypothesized that neuraxial anesthesia (NA) would provide favorable mental health profiles compared with GA after THA. METHODS: Prospectively collected Patient-Reported Outcomes Measurement Information System-10 (PROMIS) Global Mental Health (GMH) scores at preoperative baseline, and 1, 3, and 6 months after THA were accessed on 4,353 patients in the Pulmonary Embolism Prevention After HiP and KneE Replacement (PEPPER) Trial (ClinicalTrials.gov: NCT02810704). Anesthesia was categorized as: general (GA), neuraxial (NA), and neuraxial with peripheral block (NAP). The GMH was assessed longitudinally and compared between groups. RESULTS: Postoperative GMH improved (P < .05) over preoperative in every anesthetic group. Groups receiving NA had higher baseline GMH scores. Improvement in GMH was diminished after GA alone and plateaued after 1 month. Adding NA or peripheral nerve block to GA conferred additional benefit to GMH improvement. CONCLUSIONS: Patient-perceived mental health improves significantly after THA regardless of anesthetic type. Patients who have higher baseline GMH scores more commonly received NA, likely due to nonsurgical care determinants; these differences in mental wellness persisted at follow-up. Adjunctive NA or peripheral nerve block favored GMH improvement, whereas solitary GA diminished GMH improvement, which plateaued after 1 month. Substantial mental health benefits of THA may overshadow subtle differences in GMH attributable to anesthetic type.

Is the Proportion of Patients with "Successful" Outcomes After Two-stage Revision for Prosthetic Joint Infection Different When Applying the Musculoskeletal Infection Society Outcome Reporting Tool Compared with the Delphi-based Consensus Criteria?

BACKGROUND: There are a variety of criteria for defining successful treatment after two-stage exchange arthroplasty for prosthetic joint infection (PJI). To accurately assess current practices and improve techniques, it is important to first establish reliable, clinically relevant, reproducible criteria for defining persistent infection and "successful" outcomes. QUESTION/PURPOSE: Is the proportion of patients considered to have successful management of PJI after two-stage resection arthroplasty smaller using 2019 Musculoskeletal Infection Society Outcome Reporting Tool (MSIS ORT) criteria than when using a Delphi-based criterion? METHODS: Patients were retrospectively identified by Current Procedural Technology codes for resection arthroplasty with placement of an antibiotic spacer for infected THA or TKA between April 1, 2011 and January 1, 2018 at a tertiary academic institution. The initial review identified 180 procedures during this time period. Nine patients had documented transition of care outside the system, 16 did not meet the MSIS criteria for chronic PJI, and 34 patients were excluded for lack of documented 2-year follow-up. The mean follow-up duration of the final cohort of 121 procedures in 120 patients was approximately 3.7 ± 1.7 years. Forty percent (49 of 121) of the procedures were performed on the hip and 60% (72 of 121) were performed on the knee. The mean time from primary THA or TKA to explantation was 4.6 years. The mean age of the patients at the time of explantation was 66 years. The mean time from spacer placement to replantation was 119 days. The final 121 patient records were reviewed by a single reviewer and outcomes were subsequently assigned to "successful" and "unsuccessful" outcomes based on the MSIS ORT and Delphi-based consensus criterion, two previously published and validated multidimensional definition schemes. Chi-squared and t-test analyses were performed to identify differences between "successful" and "unsuccessful" outcomes with respect to patient baseline characteristics using each outcome-reporting criterion. RESULTS: Overall, the MSIS ORT classified a smaller proportion of patients as having a "successful" treatment outcome after two-stage exchange arthroplasty for PJI than the Delphi-based consensus method did (MSIS: 55% [63 of 114], Delphi: 70% [71 of 102]; relative risk 0.79 [0.65-0.98]; p = 0.03). However, there were no differences when stratified by hips (MSIS: 55% [26 of 47], Delphi: 74% [29 of 39]; relative risk 0.74 [0.54-1.02]; p = 0.07) and knees (MSIS: 55% [37 of 67], Delphi: 67% [42 of 63]; relative risk 0.83 [0.63-1.09]; p = 0.19). Notably, the disease of 16% of the patients (19 of 121) was not classifiable per the Delphi method because these patients never underwent reimplantation. CONCLUSION: The present study demonstrated that the MSIS criteria detect fewer instances of "successful" infection management after two-stage resection arthroplasty for PJI than the Delphi method in this cohort. Based on these findings, researchers and surgeons should aim for standardized reporting after intervention for PJI to allow for a better comparison of outcomes across different studies and ultimately allow for improved techniques and approaches to the treatment of PJI. LEVEL OF EVIDENCE: Level III, diagnostic study.

Generalized Anxiety Disorder: A Modifiable Risk Factor for Pain Catastrophizing After Total Joint Arthroplasty.

BACKGROUND: Patients with mood disorders undergoing total joint arthroplasty (TJA) are at increased risk for poor outcomes. This study seeks to examine the effect of anxiety disorders on pain following TJA and evaluate if anxiety disorders are a modifiable risk factor. METHODS: Between March 2019 and July 2020, 319 TJA patients had preoperative anxiety screening using the Generalized Anxiety Disorder 2-item screening tool (GAD-2) and 6-week postoperative Pain Catastrophizing Scale scores. Patients were organized into 4 cohorts based on preoperative selective serotonin reuptake inhibitor/serotonin-norepinephrine reuptake inhibitor (SSRI/SNRI) use and GAD-2 scores: Group 1: no SSRI/SNRI use and GAD-2 score <3 (control patients); Group 2: SSRI/SNRI use and GAD-2 score <3 (appropriately treated GAD patients); Group 3: no SSRI/SNRI use and GAD-2 score ≥3 (untreated GAD patients); and Group 4: SSRI/SNRI use and GAD-2 score ≥3 (poorly treated GAD patients). The cohorts underwent multivariate linear regression analysis and equivalence testing. RESULTS: Patients with preoperative GAD-2 scores ≥3 had worse postoperative pain with significantly higher average 6-week postoperative Pain Catastrophizing Scale score than patients with GAD-2 scores <3 (9.90 vs 5.19, P < .001). Patients with appropriately treated GAD and the control group had statistically equivalent postoperative pain, while patients with poorly treated or untreated GAD had worse postoperative pain. CONCLUSION: Preoperative GAD is a risk factor for poor postoperative pain control but is a modifiable risk factor when patients are appropriately treated. Screening for preoperative GAD with GAD-2 and referral for treatment may improve patient outcomes and reduce opioid consumption following TJA.

Kinesio® Tape Barrier Does Not Inhibit Intramuscular Cooling During Cryotherapy.

CONTEXT: Allied health care professionals commonly apply cryotherapy as treatment for acute musculoskeletal trauma and the associated symptoms. Understanding the impact of a tape barrier on intramuscular temperature can assist in determining treatment duration for effective cryotherapy. OBJECTIVE: To determine whether Kinesio® Tape acts as a barrier that affects intramuscular temperature during cryotherapy application. DESIGN: A repeated-measures, counterbalanced design in which the independent variable was tape application and the dependent variable was muscle temperature as measured by thermocouples placed 1 cm beneath the adipose layer. Additional covariates for robustness were body mass index and adipose thickness. SETTING: University research laboratory. PARTICIPANTS: Nineteen male college students with no contraindications to cryotherapy, no known sensitivity to Kinesio® Tape, and no reported quadriceps injury within the past 6 months. INTERVENTION: Topical cryotherapy: cubed ice bags of 1 kg and 0.5 kg. MAIN OUTCOME MEASURES: Intramuscular temperature. RESULTS: The tape barrier had no statistically significant effect on muscle temperature. The pattern of temperature change was indistinguishable between participants with and without tape application. CONCLUSIONS: Findings suggest that health care professionals can combine cryotherapy with a Kinesio® Tape application without any need for adjustments to cryotherapy duration.

Differential RNA Sequencing Implicates Sulfide as the Master Regulator of S0 Metabolism in Chlorobaculum tepidum and Other Green Sulfur Bacteria.

The green sulfur bacteria (Chlorobiaceae) are anaerobes that use electrons from reduced sulfur compounds (sulfide, S0, and thiosulfate) as electron donors for photoautotrophic growth. Chlorobaculum tepidum, the model system for the Chlorobiaceae, both produces and consumes extracellular S0 globules depending on the availability of sulfide in the environment. These physiological changes imply significant changes in gene regulation, which has been observed when sulfide is added to Cba. tepidum growing on thiosulfate. However, the underlying mechanisms driving these gene expression changes, i.e., the specific regulators and promoter elements involved, have not yet been defined. Here, differential RNA sequencing (dRNA-seq) was used to globally identify transcript start sites (TSS) that were present during growth on sulfide, biogenic S0, and thiosulfate as sole electron donors. TSS positions were used in combination with RNA-seq data from cultures growing on these same electron donors to identify both basal promoter elements and motifs associated with electron donor-dependent transcriptional regulation. These motifs were conserved across homologous Chlorobiaceae promoters. Two lines of evidence suggest that sulfide-mediated repression is the dominant regulatory mode in Cba. tepidum First, motifs associated with genes regulated by sulfide overlap key basal promoter elements. Second, deletion of the Cba. tepidum1277 (CT1277) gene, encoding a putative regulatory protein, leads to constitutive overexpression of the sulfide:quinone oxidoreductase CT1087 in the absence of sulfide. The results suggest that sulfide is the master regulator of sulfur metabolism in Cba. tepidum and the Chlorobiaceae Finally, the identification of basal promoter elements with differing strengths will further the development of synthetic biology in Cba. tepidum and perhaps other ChlorobiaceaeIMPORTANCE Elemental sulfur is a key intermediate in biogeochemical sulfur cycling. The photoautotrophic green sulfur bacterium Chlorobaculum tepidum either produces or consumes elemental sulfur depending on the availability of sulfide in the environment. Our results reveal transcriptional dynamics of Chlorobaculum tepidum on elemental sulfur and increase our understanding of the mechanisms of transcriptional regulation governing growth on different reduced sulfur compounds. This report identifies genes and sequence motifs that likely play significant roles in the production and consumption of elemental sulfur. Beyond this focused impact, this report paves the way for the development of synthetic biology in Chlorobaculum tepidum and other Chlorobiaceae by providing a comprehensive identification of promoter elements for control of gene expression, a key element of strain engineering.

Effects of 3 Different Elastic Therapeutic Taping Methods on the Subacromial Joint Space.

OBJECTIVE: The purpose of this study was to examine the effects of 3 different elastic therapeutic taping methods on the subacromial joint space in healthy adults. METHODS: Pre-/post-test laboratory study method was used in this study. Forty-eight healthy adults with no prior history of shoulder injury or surgery and no history of dominant shoulder pain in the past 6 months were enrolled in the study. Participants were placed into 3 groups (8 males and 8 females per group) on the basis of a consecutively assigned allocation design. A baseline measurement of the acromiohumeral distance (AHD) was taken by using diagnostic ultrasonography for every participant. On the basis of group assignment, participants were then taped according to the Kinesio Tape (Kinesio Tex Classic Tape) guidelines in one of 3 conditions: (1) taping of the supraspinatus from insertion to origin; (2) taping of the anterior and posterior deltoids from insertion to origin; and (3) a combination of both techniques. After a 5-minute wait period, the AHD was remeasured with the tape intervention in place, with each participant serving as his or her own control. RESULTS: Data analysis showed a statistically significant increase in AHD when using the taping technique over the anterior and posterior deltoids (Condition 2). The subacromial space increased in both males and females when the supraspinatus was taped from insertion to origin (Condition 1), but not at a statistically significant level. Condition 3, in which both taping techniques were used simultaneously, did not show an increase at a statistically significant level. CONCLUSIONS: The application of the Kinesio Tape from insertion to muscle origin of the supraspinatus or the anterior and posterior deltoid increased the subacromial joint space.

Chlorobaculum tepidum growth on biogenic S(0) as the sole photosynthetic electron donor.

The green sulfur bacteria, the Chlorobi, are phototrophic bacteria that oxidize sulfide and deposit extracellular elemental sulfur globules [S(0)]. These are subsequently consumed after sulfide is exhausted. S(0) globules from a Chlorobaculum tepidum mutant strain were purified and used to show that the wild-type strain of Cba. tepidum can grow on biogenic S(0) globules as the sole photosynthetic electron donor, i.e. in medium with no other source of reducing power. Growth yields and rates on biogenic S(0) are comparable with those previously determined for Cba. tepidum grown on sulfide as the sole electron donor. Contact between cells and S(0) was required for growth. However, only a fraction of the cell population was firmly attached to S(0) globules. Microscopic examination of cultures growing on S(0) demonstrated cell-S(0) attachment and allowed for the direct observation of S(0) globule degradation. Bulk chemical analysis, scanning electron microscopy, secondary ion mass spectrometry and SDS-PAGE indicate that Cba. tepidum biogenic S(0) globules contain carbon, oxygen and nitrogen besides S and may be associated with specific proteins. These observations suggest that current models of S(0) oxidation in the Chlorobi need to be revised to take into account the role of cell-S(0) interactions in promoting S(0) degradation.

Chlorobaculum tepidum Modulates Amino Acid Composition in Response to Energy Availability, as Revealed by a Systematic Exploration of the Energy Landscape of Phototrophic Sulfur Oxidation.

Microbial sulfur metabolism, particularly the formation and consumption of insoluble elemental sulfur (S0), is an important biogeochemical engine that has been harnessed for applications ranging from bioleaching and biomining to remediation of waste streams. Chlorobaculum tepidum, a low-light-adapted photoautolithotrophic sulfur-oxidizing bacterium, oxidizes multiple sulfur species and displays a preference for more reduced electron donors: sulfide > S0 > thiosulfate. To understand this preference in the context of light energy availability, an "energy landscape" of phototrophic sulfur oxidation was constructed by varying electron donor identity, light flux, and culture duration. Biomass and cellular parameters of C. tepidum cultures grown across this landscape were analyzed. From these data, a correction factor for colorimetric protein assays was developed, enabling more accurate biomass measurements for C. tepidum, as well as other organisms. C. tepidum's bulk amino acid composition correlated with energy landscape parameters, including a tendency toward less energetically expensive amino acids under reduced light flux. This correlation, paired with an observation of increased cell size and storage carbon production under electron-rich growth conditions, suggests that C. tepidum has evolved to cope with changing energy availability by tuning its proteome for energetic efficiency and storing compounds for leaner times. IMPORTANCE: How microbes cope with and adapt to varying energy availability is an important factor in understanding microbial ecology and in designing efficient biotechnological processes. We explored the response of a model phototrophic organism, Chlorobaculum tepidum, across a factorial experimental design that enabled simultaneous variation and analysis of multiple growth conditions, what we term the "energy landscape." C. tepidum biomass composition shifted toward less energetically expensive amino acids at low light levels. This observation provides experimental evidence for evolved efficiencies in microbial proteomes and emphasizes the role that energy flux may play in the adaptive responses of organisms. From a practical standpoint, our data suggest that bulk biomass amino acid composition could provide a simple proxy to monitor and identify energy stress in microbial systems.

The effect of a holding chamber on albuterol metered-dose inhaler product differences.

BACKGROUND: Three albuterol sulfate metered-dose inhaled (MDI) products (Ventolin HFA, Proventil HFA, and ProAir HFA) are marketed in the United States to provide the same total dose of albuterol sulfate. However, it is widely known that the fine particle dose (<5 µm) is the portion of the particle distribution that actually reaches the lungs and provides therapeutic benefit. OBJECTIVE: To examine the differences in particle size between products and how a valved holding chamber (VHC) can mitigate possible adverse effects. METHODS: Particle size distributions in each product were measured, with and without a VHC, and were analyzed by high-performance liquid chromatography. RESULTS: The only significant mean (SD) difference in total dose was between Proventil (75 [21] µg) and ProAir (107 [12] µg) (P < .01). The fine particle doses of all 3 products were significantly different: 21 (5) µg of albuterol sulfate for Ventolin, 40 (4) µg of albuterol sulfate for Proventil, and 64 (7) µg of albuterol sulfate for ProAir (P < .001 for all 3 cases). The VHC successfully removed the larger particle dose delivered by all 3 products (P ≤ .01) without reducing the fine particle dose (P > .05). CONCLUSION: Ventolin, Proventil, and ProAir should not be considered interchangeable products. In this study, the dose of albuterol sulfate likely to reach the lungs with Proventil or ProAir is 2 to 3 times that of Ventolin. As such, patients with asthma may require 3 additional puffs of Ventolin to achieve a clinical benefit similar to Proventil or ProAir. Because all 3 products contain 200 actuations, it also follows that Proventil or ProAir products may last a user 2 to 3 times longer than Ventolin.

Light-dependent sulfide oxidation in the anoxic zone of the Chesapeake Bay can be explained by small populations of phototrophic bacteria.

Microbial sulfide oxidation in aquatic environments is an important ecosystem process, as sulfide is potently toxic to aerobic organisms. Sulfide oxidation in anoxic waters can prevent the efflux of sulfide to aerobic water masses, thus mitigating toxicity. The contribution of phototrophic sulfide-oxidizing bacteria to anaerobic sulfide oxidation in the Chesapeake Bay and the redox chemistry of the stratified water column were investigated in the summers of 2011 to 2014. In 2011 and 2013, phototrophic sulfide-oxidizing bacteria closely related to Prosthecochloris species of the phylum Chlorobi were cultivated from waters sampled at and below the oxic-anoxic interface, where measured light penetration was sufficient to support populations of low-light-adapted photosynthetic bacteria. In 2012, 2013, and 2014, light-dependent sulfide loss was observed in freshly collected water column samples. In these samples, extremely low light levels caused 2- to 10-fold increases in the sulfide uptake rate over the sulfide uptake rate under dark conditions. An enrichment, CB11, dominated by Prosthecochloris species, oxidized sulfide with a Ks value of 11 µM and a Vmax value of 51 µM min(-1) (mg protein(-1)). Using these kinetic values with in situ sulfide concentrations and light fluxes, we calculated that a small population of Chlorobi similar to those in enrichment CB11 can account for the observed anaerobic light-dependent sulfide consumption activity in natural water samples. We conclude that Chlorobi play a far larger role in the Chesapeake Bay than currently appreciated. This result has potential implications for coastal anoxic waters and expanding oxygen-minimum zones as they begin to impinge on the photic zone.

The Racial School Climate Gap: Within-School Disparities in Students' Experiences of Safety, Support, and Connectedness.

This study used student and teacher survey data from over 400 middle schools in California to examine within-school racial disparities in students' experiences of school climate. It further examined the relationship between a school's racial climate gaps and achievement gaps and other school structures and norms that may help explain why some schools have larger or smaller racial disparities in student reports of climate than others. Multilevel regression results problematized the concept of a "school climate" by showing that, in an average middle school, Black and Hispanic students have less favorable experiences of safety, connectedness, relationships with adults, and opportunities for participation compared to White students. The results also show that certain racial school climate gaps vary in magnitude across middle schools, and in middle schools where these gaps are larger, the racial achievement gap is also larger. Finally, the socioeconomic status of students, student-teacher ratio, and geographic location help explain some cross-school variation in racial climate gaps. These findings have implications for how school climate in conceptualized, measured, and improved.

Chlorobaculum tepidum TLS displays a complex transcriptional response to sulfide addition.

Chlorobaculum tepidum is a green sulfur bacterium (GSB) that is a model system for phototrophic sulfur oxidation. Despite over 2 decades of research, conspicuous gaps exist in our understanding of its electron donor metabolism and regulation. RNA sequencing (RNA-seq) was used to provide a global picture of the C. tepidum transcriptome during growth on thiosulfate as the sole electron donor and at time points following the addition of sulfide to such a culture. Following sulfide addition, 121 to 150 protein-coding genes displayed significant changes in expression depending upon the time point. These changes included a rapid decrease in expression of thiosulfate and elemental sulfur oxidation genes. Genes and gene loci with increased expression included CT1087, encoding a sulfide:quinone oxidoreductase required for growth in high sulfide concentrations; a polysulfide reductase-like complex operon, psrABC (CT0496 to CT0494); and, surprisingly, a large cluster of genes involved in iron acquisition. Finally, two genes that are conserved as a cassette in anaerobic bacteria and archaea, CT1276 and CT1277, displayed a strong increase in expression. The CT1277 gene product contains a DNA-binding domain, suggesting a role for it in sulfide-dependent gene expression changes.

Identification of Bacterial Taxa Present in a Concrete Pennsylvania Bridge.

Concrete contains low microbial biomass, but some bacteria can grow in this highly alkaline environment. We used silica-based DNA extraction and 16S rRNA sequence analysis to identify the bacteria in a corroded concrete bridge sample from Bethlehem, Pennsylvania. Staphylococcus, Streptococcus, Corynebacterium, Leifsonia, Vicinamibacterales, and Actinophytocola were the most abundant genera.

Isolation and characterization of a novel biomineral stalk-forming iron-oxidizing bacterium from a circumneutral groundwater seep.

The Fe-depositing microorganism Gallionella ferruginea was first described in 1836 based on its association with Fe-rich environments and its distinctive morphology. Since then, this morphology has been widely used to identify G. ferruginea. Researchers have isolated several Fe-oxidizing bacteria (FeOB) related to Gallionella; however, few isolates have produced organized extracellular biomineral structures, and of these, only one stalk former has a sequenced 16S rRNA gene, listed as G. ferruginea in the GenBank database. Here we report the isolation and characterization of a novel stalk-forming Fe-oxidizing bacterium, strain R-1, from a freshwater Fe seep. Despite a strong morphological similarity to G. ferruginea, this isolate has only 93.55% 16S rRNA gene sequence similarity with the previously determined sequence. R-1 only grows on Fe(II) substrates, at pH 5.6 to 7.0 and from 10°C to 35°C, with a doubling time of ∼15 h at pH 6.3 and 22°C. It is a Betaproteobacterium, most closely related to uncultured bacteria from microaerobic Fe(II)-rich groundwater springs. The most closely related isolates are Sideroxydans spp. (94.05-94.42% sequence similarity), FeOB that are not known to produce morphologically distinct minerals. To our knowledge, this is the first reported stalk-forming freshwater FeOB isolate distinct from Gallionella.

Volatile dimethyl polonium produced by aerobic marine microorganisms.

The production of volatile polonium (Po(v)), a naturally occurring radioactive element, by pure cultures of aerobic marine tellurite-resistant microorganisms was investigated. Rhodotorula mucilaginosa, a carotogenic yeast, and a Bacillus sp. strain, a Gram-positive bacterium, generated approximately one and 2 orders of magnitude, respectively, greater amounts of Po(v) compared to the other organisms tested. Gas chromatography-inductively coupled plasma-mass spectrometry (GC-ICP-MS) analysis identified dimethyl polonide (DMPo) as the predominant volatile Po compound in culture headspace of the yeast. This species assignment is based on the exact relation between GC retention times and boiling points of this and other Group VI B analogues (S, Se, and Te). The extent of the biotic Po(v) production correlates exponentially with elevated particulate Po (Po(p)): dissolved Po (Po(aq)) ratios in the cultures, consistent with efficient Po bioaccumulation. Further experimentation demonstrated that some abiotic Po(v) generation is possible. However, high-level Po(v) generation in these cultures is predominantly biotic.

Adaptations to submarine hydrothermal environments exemplified by the genome of Nautilia profundicola.

Submarine hydrothermal vents are model systems for the Archaean Earth environment, and some sites maintain conditions that may have favored the formation and evolution of cellular life. Vents are typified by rapid fluctuations in temperature and redox potential that impose a strong selective pressure on resident microbial communities. Nautilia profundicola strain Am-H is a moderately thermophilic, deeply-branching Epsilonproteobacterium found free-living at hydrothermal vents and is a member of the microbial mass on the dorsal surface of vent polychaete, Alvinella pompejana. Analysis of the 1.7-Mbp genome of N. profundicola uncovered adaptations to the vent environment--some unique and some shared with other Epsilonproteobacterial genomes. The major findings included: (1) a diverse suite of hydrogenases coupled to a relatively simple electron transport chain, (2) numerous stress response systems, (3) a novel predicted nitrate assimilation pathway with hydroxylamine as a key intermediate, and (4) a gene (rgy) encoding the hallmark protein for hyperthermophilic growth, reverse gyrase. Additional experiments indicated that expression of rgy in strain Am-H was induced over 100-fold with a 20 degrees C increase above the optimal growth temperature of this bacterium and that closely related rgy genes are present and expressed in bacterial communities residing in geographically distinct thermophilic environments. N. profundicola, therefore, is a model Epsilonproteobacterium that contains all the genes necessary for life in the extreme conditions widely believed to reflect those in the Archaean biosphere--anaerobic, sulfur, H2- and CO2-rich, with fluctuating redox potentials and temperatures. In addition, reverse gyrase appears to be an important and common adaptation for mesophiles and moderate thermophiles that inhabit ecological niches characterized by rapid and frequent temperature fluctuations and, as such, can no longer be considered a unique feature of hyperthermophiles.

Function, structure, and evolution of the RubisCO-like proteins and their RubisCO homologs.

About 30 years have now passed since it was discovered that microbes synthesize RubisCO molecules that differ from the typical plant paradigm. RubisCOs of forms I, II, and III catalyze CO(2) fixation reactions, albeit for potentially different physiological purposes, while the RubisCO-like protein (RLP) (form IV RubisCO) has evolved, thus far at least, to catalyze reactions that are important for sulfur metabolism. RubisCO is the major global CO(2) fixation catalyst, and RLP is a somewhat related protein, exemplified by the fact that some of the latter proteins, along with RubisCO, catalyze similar enolization reactions as a part of their respective catalytic mechanisms. RLP in some organisms catalyzes a key reaction of a methionine salvage pathway, while in green sulfur bacteria, RLP plays a role in oxidative thiosulfate metabolism. In many organisms, the function of RLP is unknown. Indeed, there now appear to be at least six different clades of RLP molecules found in nature. Consideration of the many RubisCO (forms I, II, and III) and RLP (form IV) sequences in the database has subsequently led to a coherent picture of how these proteins may have evolved, with a form III RubisCO arising from the Methanomicrobia as the most likely ultimate source of all RubisCO and RLP lineages. In addition, structure-function analyses of RLP and RubisCO have provided information as to how the active sites of these proteins have evolved for their specific functions.