Immunological and molecular diagnostic techniques in fish health: present and future prospectus.

Fish health management is critical to aquaculture and fisheries as it directly affects sustainability and productivity. Fish disease diagnosis has taken a massive stride because of advances in immunological and molecular diagnostic tools which provide a sensitive, quick, and accurate means of identifying diseases. This review presents an overview of the main molecular and immunological diagnostic methods for determining the health of fish. The immunological techniques help to diagnose different fish diseases by detecting specific antigens and antibodies. The application of immunological techniques to vaccine development is also examined in this review. The genetic identification of pathogens is made possible by molecular diagnostic techniques that enable the precise identification of bacterial, viral, and parasitic organisms in addition to evaluating host reactions and genetic variation associated with resistance to disease. The combination of molecular and immunological methods has resulted in the creation of novel techniques for thorough evaluation of fish health. These developments improve treatment measures, pathogen identification and provide new information about the variables affecting fish health, such as genetic predispositions and environmental stresses. In the framework of sustainable fish farming and fisheries management, this paper focuses on the importance of these diagnostic techniques that play a crucial role in protecting fish populations and the aquatic habitats. This review also examines the present and potential future directions in immunological and molecular diagnostic techniques in fish health.

Assessing vaccine hesitancy among health-care workers in Jammu and Kashmir: A cross-sectional study.

BACKGROUND: The World Health Organization declared vaccine hesitancy as one of the planet's top 10 global health threats in 2019. With the rollout of the coronavirus disease-19 (COVID-19) vaccines, a survey was conducted to find out the hesitancy and the apprehensions that come along with taking COVID-19 vaccines among health-care workers (HCWs). MATERIALS AND METHODS: This was an online cross-sectional survey which was developed and shared through social media platforms among the HCWs of Kashmir. The survey captured demographic data and used a validated hesitancy measurement tool from January 2021 to February 2021. The data were analyzed by descriptive statistics and multivariable logistic regression using Stata 15 (Stata Corp. 2017. Stata Statistical Software: Release 15. College Station, TX: Stata Corp LLC). RESULTS: Willingness to take the COVID-19 vaccine when available was seen in 67.7% of the HCWs. Overall, 9.59% of respondents reported unwillingness to receive a vaccine for COVID-19, while 22.7% were unsure. The most commonly cited reason for willingness to get vaccinated was an understanding of the disease and vaccination, as reported by 81.5%. Being single was significantly related to an increased risk of vaccine hesitancy (adjusted odds ratio = 5.27, 95% confidence interval: 2.07-13.40). Among vaccine attitudes, concerns about the safety of the vaccine, unforeseen problems in children, and possible unknown future adverse effects of the vaccine were the most important determinants of unwillingness. CONCLUSIONS: A significant proportion of the HCWs showed vaccine hesitancy to the COVID-19 vaccine. Hesitancy attitudes were almost always driven by concern around the vaccine safety. States and health-care authorities need to recognize the massive trust deficit around the Covid-19 vaccine and use the popular media used by people to share credible and reliable information.

Vaccine hesitancy and coronavirus disease-19: Where do we stand?

BACKGROUND: Vaccine hesitancy is seen, globally, as a major factor that will determine future coronavirus disease-19 (COVID-19) spread and its effective management. This study aimed to identify COVID-19 vaccine perception, acceptance, confidence, hesitancy, and barriers among the general population. MATERIALS AND METHODS: This was an online survey which was developed and shared through social media platforms among the general population of Kashmir. The survey captured demographic data and used a validated hesitancy measurement tool. We analyzed the data using descriptive statistics and multivariable logistic regression using Stata 15 (Stata Corp. 2017. Stata Statistical Software: Release 15. College Station, TX, USA: Stata Corp LLC). RESULTS: A total of 835 responses were received. Most participants were males, with females compromising of 19.5% participants. 65.1% of participants were in the age group of 30-50, whereas 19.2% were below 30 years of age. 52.70% of respondents were willing to take the vaccine when available, while 32.5% of respondents were unsure about their decision of inoculation. The most cited reason for willingness to get vaccinated was an understanding of the disease and vaccination. 41.70% felt that the vaccines developed against COVID-19 have not been fully tested; therefore, concerns around the safety and its longer-term side effects were the reasons cited. Public health messaging should be tailored to address these concerns. CONCLUSIONS: Vaccine hesitancy is a global threat undermining the control of preventable infections. The government should take proactive steps to address the factors that may potentially impact the benefits expected from the introduction of a COVID-19 vaccine in the union territory.

Psychiatric comorbidities among COVID-19 survivors in North India: A cross-sectional study.

BACKGROUND: The coronavirus disease-19 (COVID-19) emerged from China and rapidly spread to many other countries all over the world. This study aimed to assess the prevalence of anxiety, depression, posttraumatic stress disorder, and obsessive-compulsive (OC) symptoms among COVID-19 survivors after their discharge from the COVID-19 treatment center. MATERIALS AND METHODS: This was a cross-sectional, hospital-based study performed among 119 COVID-19 survivors. The Hospital Anxiety and Depression Scale (HADS) was used to measure anxiety and depression. Posttraumatic Stress Disorder (PTSD)-Checklist (PCL) and Brief OC Scale were used to measure PTSD and OC symptoms. Data were analyzed by descriptive and inferential statistics using the SPSS (IBM Corp. Released 2015 version 23.0). RESULTS: The mean anxiety, depression, and PTSD scores were, 7.12 ± 0.68, 8.08 ± 0.22, and 19.78 ± 0.88, respectively. Based on cutoff scores, the prevalence of anxiety, depression, and PTSD among COVID-19 survivors was n = 53, 44.54%; n = 73, 61.34%; and n = 30, 25.21%, respectively. Older COVID-19 survivors (≥50 years) were more likely to show symptoms of depression and anxiety (P < 0.001) compared to younger ones. Furthermore, COVID-19 survivors who were ≥50 years of age experienced a greater level of PTSD compared to younger ones; similar trends were seen in those experiencing OC symptoms. In the present study, n = 98 (82.4%) were obsessed with fears of contamination and an equal number had compulsive handwashing. CONCLUSION: Anxiety, depression, PTSD, and OC symptoms are common among the COVID-19 survivors and that underscores the need to diagnose and manage mental health morbidities among these survivors long after their recovery from COVID-19.

A Comparative Study of Aripiprazole, Olanzapine, and L-Methylfolate Augmentation in Treatment Resistant Obsessive-Compulsive Disorder.

About half of the patients with Obsessive-compulsive disorder (OCD) do not respond to serotonin reuptake inhibitors (SRIs) or have a partial improvement in their symptoms. This study aimed to compare the efficiency and safety of aripiprazole, olanzapine, and L-methyl folate in patients with resistant OCD. The study consisted of an open-label prospective phase of 12-weeks to ascertain resistance to SRIs and a second 6-week open-label addition phase for non or, partial responders of the first phase. One-hundred-fifteen patients entered the 16-week open-label phase. Fifty patients (43.47%) responded to the SRIs monotherapy, two patients developed adverse effects and another three were lost to the follow up. Sixty patients (52.2%) were considered treatment-resistant and entered the 6-week open-label aripiprazole, olanzapine, or L-methyl folate addition phase; Patients showed a significant improvement over 6-week study period in olanzapine and aripiprazole group as measured by YBOCS total score (p < 0.001) while there was no change in the L-methyl folate group at the end as compared with baseline (p = 0.150). Clinical Global Impression-Severity decreased from 4.90 to 2.90 in olanzapine and aripiprazole group at the end of 6 weeks while there was no change in the L-methyl folate group. The CGI-I was significant in the olanzapine and aripiprazole group (p < 0.001) while it was insignificant in the L-methyl folate group (p = 0.088). Augmentation of SRIs with olanzapine or aripiprazole could be a promising option for resistant OCD. L-methyl folate though shown to be effective in resistant depression was not effective in treatment resistant OCD.

Correction: Stigma in coronavirus disease-19 survivors in Kashmir, India: A cross-sectional exploratory study.

[This corrects the article DOI: 10.1371/journal.pone.0240152.].

Stigma in coronavirus disease-19 survivors in Kashmir, India: A cross-sectional exploratory study.

BACKGROUND: Coronavirus disease-19 (COVID-19) has not only spawned a lot of stigma and discrimination towards its survivors but also to their corpses. We aimed to assess the magnitude and correlates of stigma in these survivors, on return to their communities. METHODS: This was a cross-sectional, hospital-based, exploratory study conducted by the postgraduate department of psychiatry, in collaboration with the postgraduate department of chest medicine, Govt. medical college, Srinagar. The study was performed among COVID-19 survivors, who attended the outpatient department after their discharge from the hospital. Socio-demographic characteristics were recorded through semi-structured proforma. Stigma was measured by the stigma questionnaire. Data was analyzed using descriptive statistics and regression analysis. RESULTS: A total of 91 survivors consented to participate in the study. Almost half (46.2%) of them were in the age group of 30-49 years and close to two-thirds (68.1%) were males. About three-fourths (74.7%) were from the urban background. The mean time from hospital discharge to study entry was 11.7±5.1 [Range(R) = 7-21] days. 98% of survivors provided at least one stigma endorsing response and the total mean stigma score was 28.5±7.1[R = 6-39]. The mean stigma sub-scores were highest for enacted stigma (7.6±1.8) [R = 2-9] and externalized stigma (15.0±4.1) [R = 1-20]. Enacted stigma was significantly high in males as compared to females. Enacted stigma and internalized stigma were both associated with education. Enacted stigma, externalized stigma, disclosure concerns, and total stigma was significantly associated with the occupation. Being unemployed and time since discharge were identified as independent predictors of total stigma. CONCLUSION: Our study results showed high levels of enacted and externalized stigma among COVID-19 survivors. Enacted stigma was more among males and in those who were highly educated. Survivor centered and community-driven anti-stigma programs are the need of the hour to promote the recovery and community re-integration of these survivors.

First Observation of Multiple Transverse Wobbling Bands of Different Kinds in

We report the first observation of two wobbling bands in ^{183}Au, both of which were interpreted as the transverse wobbling (TW) band but with different behavior of their wobbling energies as a function of spin. It increases (decreases) with spin for the positive (negative) parity configuration. The crucial evidence for the wobbling nature of the bands, dominance of the E2 component in the ΔI=1 transitions between the partner bands, is provided by the simultaneous measurements of directional correlation from the oriented states ratio and the linear polarization of the γ rays. Particle rotor model calculations with triaxial deformation reproduce the experimental data well. A value of spin, I_{m}, has been determined for the observed TW bands below which the wobbling energy increases and above which it decreases with spin. The nucleus ^{183}Au is, so far, the only nucleus in which both the increasing and the decreasing parts are observed and thus gives the experimental evidence of the complete transverse wobbling phenomenon.

Thyroid hormone levels and Thyroid Hormone Levels and Ultrasonographic Changes in the Thyroid Gland of Patients on Long-Term Lithium Treatment for Affective Disorders: A Controlled Study.

BACKGROUND: Although lithium is known to cause thyroid dysfunction and increased thyroid gland volume, clinical examination and biochemical assessment are fundamental to thyroid workup of patients on lithium treatment. We aimed to determine thyroid gland volume and the Thyroid hormone levels of patients who have been receiving lithium treatment for affective disorders in comparison to voluntary healthy controls. METHODS: This was a cross-sectional, hospital-based observational study which was performed in 43 patients on long-term lithium treatment for bipolar disorder, major depressive and schizoaffective disorders. Patients with documented continuous and adequate serum lithium levels for more than or equal to 6 months recruited consecutively underwent the ultrasonographic examination of the thyroid gland. Ultrasonographic examinations were also done in all gender- and age-matched healthy controls. All cases and controls underwent biochemical thyroid function tests. RESULTS: There were no statistically significant differences in gender (P = 0.198; Chi-square = 1.654) of cases and controls. Most of the cases were married, maximum number of them unemployed and belonged to the lower socioeconomic status. Total thyroid volume was significantly greater in the lithium-treated group than the controls (9.40 ± 1.41 vs. 4.79 ± 0.45). Clinical inspection and palpation only detected goiter in six (n = 6, 13.95%) of patients on lithium and none among controls. The mean triiodothyronine, mean thyroxine, and mean scores for thyroid-stimulating hormone were significantly increased in patients receiving lithium therapy as compared to controls. CONCLUSION: It would seem wise from a clinical point of view to include ultrasonographic examination of the thyroid gland as part of the standard thyroid workup before initiating lithium treatment.

Healthcare Providers on the Frontline: A Quantitative Investigation of the Stress and Recent Onset Psychological Impact of Delivering Health Care Services During COVID-19 in Kashmir.

BACKGROUND: Frontline healthcare workers (FHCWs) are at an increased risk of contracting COVID-19. We aimed to assess the stress and psychological impact of the COVID-19 pandemic among FHCWs. METHODS: This was an exploratory hospital-based study. A semistructured e-questionnaire was developed and shared through emails, WhatsApp groups, Facebook, and Twitter. The study instruments used were stress questionnaire and the impact of event scale-revised. RESULTS: We received 133 valid responses. A total of 81 (61.4%) of the respondents were single, 74 (55.6) were male, 70 (52.6%) were between 20 and 29 years of age, and 91 (68.4%) were from urban background. A total of 83 (62.4%) of respondents were doctors and 28 (21.1%) were registered nurses. A total of 36 (27.1%) were posted in emergency and 34 (25.6%) were in the in-patient department. Feeling sad and pessimistic, feeling of being avoided by others, the burden of change in the quality of work, and worrying whether the family will be cared for in their absence were significantly more in nurses as compared to the doctors. Stress due to burden in an increase in the quantity of work was seen more in FHCWs working in the swab collection center as compared to those working in the in-patient department, emergency, or theaters. Severe psychological impact was seen in 81 (60.9%) of FHCWs. The psychological impact was significantly more in males and in those who were married. It was also significantly related to the place of posting. CONCLUSION: More than half of the FHCWs had a severe psychological impact owing to COVID-19. The psychological impact was more in males and those who were married, and it was related to the place of posting of the FHCWs. Nurses had significantly higher stress as compared to doctors.

The Pattern of Psychiatric Morbidity in Chronic Obstructive Pulmonary Disease: A Cross-Sectional, Case-Control Study from a Tertiary Care Hospital in Kashmir, North India.

INTRODUCTION: Psychiatric morbidity has an increased prevalence in chronic obstructive pulmonary disease (COPD). Patients overall psychosocial status plays an important role in the development of depression which, when major, is said to occur in 19%-42% of cases of COPD. We aimed to study patterns of psychosocial issues in patients with COPD. MATERIALS AND METHODS: This study was conducted over a period of 6 months in an Outpatient Department of Government Chest Disease Hospital Srinagar. A total of 100 COPD patients and 100 sex- and age-matched controls were included in this study and compared. The diagnosis of COPD was assessed by spirometry. Patterns of psychiatric morbidities were assessed using the Mini-International Neuropsychiatric Interview. RESULTS: The frequency of psychiatric comorbidities was significantly higher (P < 0.001) in COPD patients (47%) as compared to controls (12%). The highest frequency of psychiatric morbidities in COPD patients was major depressive episode in 28% in comparison to 9% of controls. Other morbidities include panic disorder, dysthymia, generalized anxiety disorder, and suicidality. CONCLUSION: The frequency of psychiatric morbidities is increased in COPD patients as compared to controls. We recommend that all patients with COPD should be screened for psychiatric morbidity as there is enough scope for psychiatric services to be made available to these patients.

A prospective study on quality of life in patients with pulmonary tuberculosis at a tertiary care hospital in Kashmir, Northern India.

BACKGROUND: Pulmonary Tuberculosis (PTB) is a contagious, airborne infection that destroys when M. tuberculosis primarily attacks the lungs. PTB is curable with an early diagnosis and antibiotic treatment. Stigmatization and negative emotions resulting from the illness could result in long term impairment of patients psychological well being which may result in work absenteeism resulting in loss of productivity and reduced monthly income. METHODS: This was a prospective study which was conducted over a period of one and half year. A total of 198 patients were recruited for the study. Quality Of Life (QOL) was assessed at baseline and at the end of intensive phase. For QOL WHO based QOLBREF was used. RESULTS: In the present study patients scored lowest in the baseline physical (8.36 ± 1.60) followed by the psychological domain (10.40 ± 1.72) however at the end of intensive phase both physical (11.98 ± 1.70) and psychological (12.75 ± 1.) domains improved very much and the difference was statistically significant. CONCLUSION: We conclude that HRQOL is significantly reduced in patients with PTB, and that it improves rapidly and significantly with DOTS-based intensive phase of treatment. Special focus on reduction of stigmatization should be given in the management of TB to reduce the psychological distress.

Undescended Testes and Laparoscopy: Experience from the Developing World.

BACKGROUND: Cryptorchidism or undescended testes is the most common disorder of the male endocrine glands in children. With the advancements in laparoscopic techniques and instruments, laparoscopic orchidopexy has become the standard procedure in the management of nonpalpable undescended testes. AIM: To evaluate and determine the therapeutic role, sensitivity, and specificity of laparoscopy in localizing nonpalpable testes and the mean operative time, the conversion rate (and reasons thereof), postoperative wound infection, postoperative stay, and time taken for return to daily activities following laparoscopic orchidopexy or orchidectomy. MATERIALS AND METHODS: This was a prospective study carried out in the Postgraduate Department of Surgery, Government Medical College, Srinagar, J&K, India, from May 2008 to August 2011. All patients who presented to the outpatient department with complaints of absent testes were examined, and the ones with nonpalpable testes were included in the study. RESULTS: The mean operative time for bilateral and unilateral nonpalpable testis was 102.76 and 53.67 minutes, respectively. Minor postoperative wound infections were noted in 4 of our patients. Mean duration of hospital stay was 14.23 hrs for unilateral cases and 16.27 hrs for bilateral cases. Patients who underwent laparoscopic orchidopexy resumed their normal activities within 4 ± 1 days. CONCLUSION: Laparoscopy clearly demonstrates the anatomy and provides visual information upon which a definitive decision can be made for further management of the undescended nonpalpable testis.

The Pattern of Psychiatric Morbidity in an Outpatient Child Psychiatry Clinic: A Cross-sectional, Descriptive Study from a Tertiary Care Hospital in Kashmir, North India.

BACKGROUND: Psychiatric disorders are ubiquitous and affect not only adults but also children and adolescents. The age factor plays an important role in the pattern of these psychiatric disorders. The objective of our study was to find the pattern of psychiatric morbidity in children and adolescents at the child and adolescent outpatient service of a tertiary care hospital. MATERIALS AND METHODS: A semi-structured questionnaire was used to record the sociodemographic status. The state of mental health and psychiatric morbidity was assessed after a thorough clinical assessment. Intelligence quotient was assessed by a clinical psychologist as and when needed. All the diagnoses were made on the basis of Diagnostic and Statistical Manual of Mental Disorders, 4th Edition, Text Revision criteria. RESULTS: A total of 529 patients were included. Most patients belonged to the age group of 6-16 years (70.5%). Boys (67.9%) outnumbered girls. Most of the patients were from rural background (56.7%) and from nuclear families (53%). Attention-deficit hyperactivity disorder (31%) and mental retardation (29%) were the most frequent diagnoses, followed by pervasive developmental disorders (10%). Comorbidity was present in about 18% of our patients. CONCLUSION: The child psychiatry is gaining acceptance, and children and adolescents with minor mental health issues are being identified and referred for specialized services.

Sulfur oxidation to sulfate coupled with electron transfer to electrodes by Desulfuromonas strain TZ1.

Microbial oxidation of elemental sulfur with an electrode serving as the electron acceptor is of interest because this may play an important role in the recovery of electrons from sulfidic wastes and for current production in marine benthic microbial fuel cells. Enrichments initiated with a marine sediment inoculum, with elemental sulfur as the electron donor and a positively poised (+300 mV versus Ag/AgCl) anode as the electron acceptor, yielded an anode biofilm with a diversity of micro-organisms, including Thiobacillus, Sulfurimonas, Pseudomonas, Clostridium and Desulfuromonas species. Further enrichment of the anode biofilm inoculum in medium with elemental sulfur as the electron donor and Fe(III) oxide as the electron acceptor, followed by isolation in solidified sulfur/Fe(III) medium yielded a strain of Desulfuromonas, designated strain TZ1. Strain TZ1 effectively oxidized elemental sulfur to sulfate with an anode serving as the sole electron acceptor, at rates faster than Desulfobulbus propionicus, the only other organism in pure culture previously shown to oxidize S° with current production. The abundance of Desulfuromonas species enriched on the anodes of marine benthic fuel cells has previously been interpreted as acetate oxidation driving current production, but the results presented here suggest that sulfur-driven current production is a likely alternative.

Hematobiochemical evaluation of dermal subacute cypermethrin toxicity in buffalo calves.

Dermal exposure of cypermethrin, a type II synthetic pyrethroid insecticide, at dose rate of 0.25% for 14 consecutive days produced mild signs of toxicity in buffalo calves. It produced significant elevation in the levels of alanine aminotransferase (ALT; 39.5%), aspartate aminotransferase (AST; 32.0%), blood urea nitrogen (BUN; 57.7%), and plasma creatinine (30.0%). Cypermethrin also produced significant decrease in the hemoglobin (Hb) concentration (5.4%), packed cell volume (PCV; 3.4%), and total erythrocytic count (4.0%). Additionally, there was a significant increase in erythrocytic sedimentation rate (ESR; 3.1%). On the basis of the present study, it can be concluded that cypermethrin induces significant biochemical and hematological alterations in buffalo calves when exposed dermally.

Comparative evaluation of oral and dermal cypermethrin exposure on antioxidant profile in Bubalus bubalis.

Cypermethrin, a type II synthetic pyrethroid insecticide, @ 0.5mg/kg/day for 14 consecutive weeks produced mild signs of toxicity in buffalo calves. Significant changes were observed in various antioxidant parameters in blood. There was a marked increase in the extent of lipid peroxidation (33.9%) and enzymic activity of glutathione peroxidase (6.7%), superoxide dismutase (35.0%), catalase (43.7%), glutathione-S-transferase (64.4%), glutathione reductase (36.7%) and glucose-6-phosphate dehydrogenase (32.1%). A significant decrease in blood glutathione (16.7%), total antioxidant activity (45.4%) and vitamin E (40.8%) was observed and no significant effect was found on blood selenium levels. However, the extent of lipid peroxidation (42%) and the depletion of glutathione (28.8%) was greater after dermal sub-acute toxicity of cypermethrin (0.25%) for 14 consecutive days. Similarly, it was observed that the incline in the enzymic activity of glutathione peroxidase (29.7%), superoxide dismutase (38.3%) and glutathione reductase (38.3%) was higher in dermally cypermethrin exposed animals. Thus, the present investigation contemplates that oxidative stress is the important mechanisms involved in cypermethrin-induced toxicity and the oxidative insult produced by dermal route is more severe as compared to oral intoxication.

The Rnf complex of Clostridium ljungdahlii is a proton-translocating ferredoxin:NAD+ oxidoreductase essential for autotrophic growth.

UNLABELLED: It has been predicted that the Rnf complex of Clostridium ljungdahlii is a proton-translocating ferredoxin:NAD(+) oxidoreductase which contributes to ATP synthesis by an H(+)-translocating ATPase under both autotrophic and heterotrophic growth conditions. The recent development of methods for genetic manipulation of C. ljungdahlii made it possible to evaluate the possible role of the Rnf complex in energy conservation. Disruption of the C. ljungdahlii rnf operon inhibited autotrophic growth. ATP synthesis, proton gradient, membrane potential, and proton motive force collapsed in the Rnf-deficient mutant with H(2) as the electron source and CO(2) as the electron acceptor. Heterotrophic growth was hindered in the absence of a functional Rnf complex, as ATP synthesis, proton gradient, and proton motive force were significantly reduced with fructose as the electron donor. Growth of the Rnf-deficient mutant was also inhibited when no source of fixed nitrogen was provided. These results demonstrate that the Rnf complex of C. ljungdahlii is responsible for translocation of protons across the membrane to elicit energy conservation during acetogenesis and is a multifunctional device also implicated in nitrogen fixation. IMPORTANCE: Mechanisms for energy conservation in the acetogen Clostridium ljungdahlii are of interest because of its potential value as a chassis for the production of biocommodities with novel electron donors such as carbon monoxide, syngas, and electrons derived from electrodes. Characterizing the components implicated in the chemiosmotic ATP synthesis during acetogenesis by C. ljungdahlii is a prerequisite for the development of highly productive strains. The Rnf complex has been considered the prime candidate to be the pump responsible for the formation of an ion gradient coupled with ATP synthesis in multiple acetogens. However, experimental evidence for a proton-pumping Rnf complex has been lacking. This study establishes the C. ljungdahlii Rnf complex as a proton-translocating ferredoxin:NAD(+) oxidoreductase and demonstrates that C. ljungdahlii has the potential of becoming a model organism to study proton translocation, electron transport, and other functions of the Rnf complex in energy conservation or other processes.

Population dynamics of a single-stage sulfidogenic bioreactor treating synthetic zinc-containing waste streams.

Waste streams from industrial processes such as metal smelting or mining contain high concentrations of sulfate and metals with low pH. Dissimilatory sulfate reduction carried out by sulfate-reducing bacteria (SRB) at low pH can combine sulfate reduction with metal-sulfide precipitation and thus open possibilities for selective metal recovery. This study investigates the microbial diversity and population changes of a single-stage sulfidogenic gas-lift bioreactor treating synthetic zinc-rich waste water at pH 5.5 by denaturing gradient gel electrophoresis of 16S rRNA gene fragments and quantitative polymerase chain reaction. The results indicate the presence of a diverse range of phylogenetic groups with the predominant microbial populations belonging to the Desulfovibrionaceae from delta-Proteobacteria. Desulfovibrio desulfuricans-like populations were the most abundant among the SRB during the three stable phases of varying sulfide and zinc concentrations and increased from 13% to 54% of the total bacterial populations over time. The second largest group was Desulfovibrio marrakechensis-like SRB that increased from 1% to about 10% with decreasing sulfide concentrations. Desulfovibrio aminophilus-like populations were the only SRB to decrease in numbers with decreasing sulfide concentrations. However, their population was <1% of the total bacterial population in the reactor at all analyzed time points. The number of dissimilatory sulfate reductase (DsrA) gene copies per number of SRB cells decreased from 3.5 to 2 DsrA copies when the sulfide concentration was reduced, suggesting that the cells' sulfate-reducing capacity was also lowered. This study has identified the species present in a single-stage sulfidogenic bioreactor treating zinc-rich wastewater at low pH and provides insights into the microbial ecology of this biotechnological process.

Selective recovery of nickel over iron from a nickel-iron solution using microbial sulfate reduction in a gas-lift bioreactor.

Process streams with high concentrations of metals and sulfate are characteristic for the mining and metallurgical industries. This study aims to selectively recover nickel from a nickel-iron-containing solution at pH 5.0 using a single stage bioreactor that simultaneously combines low pH sulfate reduction and metal-sulfide formation. The results show that nickel was selectively precipitated in the bioreactor at pH 5.0 and the precipitates consisted of >or=83% of the nickel content. The nickel-iron precipitates were partly crystalline and had a metal/sulfur ratio of 1, suggesting these precipitates were NiS and FeS. Experiments focusing on nickel recovery at pH 5.0 and 5.5 reached a recovery of >99.9%, resulting in a nickel effluent concentration<0.05 microM. The mixed microbial population included known sulfate reducers and acetogens. This study shows that selective metal precipitation in a single stage sulfate reducing bioreactor operated at low pH has the potential to produce metal-sulfides that can be used by the metallurgical industry as a resource for metal production.