Growth kinetics of an indigenous mixed microbial consortium during phenol degradation in a batch reactor

Biodegradation of phenol by a mixed microbial culture, isolated from a sewage treatment plant, was investigated in batch shake flasks. A minimum concentration of 100 and a maximum of 800 mg 1(-1) of phenol in the media were adapted in the degradation study. The phenol degradation rate varied largely and was less than 10 mg l(-1)h(-1) at both extremes of the initial concentrations in the media. The degradation rate was maximum 15.7 mg l(-1)h(-1) at 400 mg l(-1) phenol. The culture followed substrate inhibition kinetics and the specific growth rate were fitted to Haldane and Han-Levenspiel models. Between the two models the Han-Levenspiel was found to be a better fit with a root mean square error of 0.0211. The biokinetics constants estimated using these models showed good potential of the mixed microbial culture in phenol degradation.     

Crystal structure of binary and ternary complexes of serine hydroxymethyltransferase from Bacillus stearothermophilus: insights into the catalytic mechanism

Serine hydroxymethyltransferase (SHMT), a member of the alpha-class of pyridoxal phosphate-dependent enzymes, catalyzes the reversible conversion of serine to glycine and tetrahydrofolate to 5,10-methylene tetrahydrofolate. We present here the crystal structures of the native enzyme and its complexes with serine, glycine, glycine, and 5-formyl tetrahydrofolate (FTHF) from Bacillus stearothermophilus. The first structure of the serine-bound form of SHMT allows identification of residues involved in serine binding and catalysis. The SHMT-serine complex does not show any significant conformational change compared with the native enzyme, contrary to that expected for a conversion from an "open" to "closed" form of the enzyme. However, the ternary complex with FTHF and glycine shows the reported conformational changes. In contrast to the Escherichia coli enzyme, this complex shows asymmetric binding of the FTHF to the two monomers within the dimer in a way similar to the murine SHMT. Comparison of the ternary complex with the native enzyme reveals the structural basis for the conformational change and asymmetric binding of FTHF. The four structures presented here correspond to the various reaction intermediates of the catalytic pathway and provide evidence for a direct displacement mechanism for the hydroxymethyl transfer rather than a retroaldol cleavage.     

Metabolized‐Water Breeding Diseases in Urban India: Sociospatiality of Water Problems and Health Burden in Ahmedabad City

Studies on urban metabolism have provided important insights in the material and sociopolitical issues associated with the flow of water. However, there is a dearth of studies that reveal how infrastructure, as a hybrid of social and material construct, facilitates disease emergence. The article brings together urban metabolism, political ecology, and anthropological studies to examine the social construction and reconstruction of the material flow through everyday practices for addressing the water problem and its health burden in Ahmedabad city. The article georeferences the water problems and occurrence of diseases and, through interviews, documents Ahmedabad's sociospatial characteristics of water problems and health burden in two case study wards. Through a situated understanding of the everyday practices, the infrastructure is exposed through leakages, reveals the citizens desire for better water quality, and struggle to gain access to water using diverse ‘pressure’ tactics. It is these social‐material constructs of water that give structure and coherence to urban space, which spatially coincides with the occurrence of diseases. It reveals the sociopolitical drivers of the water problems and identifies different hypotheses of the hotspots of disease emergences. The methodology offers a way forward for researchers and development agencies to improve the surveillance and monitoring of water infrastructure and public health through an incremental approach that takes into consideration the diffuse interplay of power by diverse actors. It charts out avenues for building on the urban metabolism by emphasizing the importance of examining the sociospatiality of the everyday practices for improving resource use efficiencies in cities of rapidly growing economies.     

Sequence and structural analysis of fibronectin‐binding protein reveals importance of multiple intrinsic disordered tandem repeats

The location of certain amino acid sequences like repeats along the polypeptide chain is very important in the context of forming the overall shape of the protein molecule which in fact determines its function. In gram‐positive bacteria, fibronectin‐binding protein (FnBP) is one such repeat containing protein, and it is a cell wall‐attached protein responsible for various acute infections in human. Several studies on sequence, structure, and function of fibronectin‐binding regions of FnBPs were reported; however, no detailed study was carried out on the full‐length protein sequence. In the present study, we have made a thorough sequence and structure analysis on FnBP_A of Staphylococcus aureus and explored the presence of dual ligand‐binding ability of fibrinogen (fg)‐binding region and its molecular recognition processes. Multiple sequence alignment and protein‐protein docking analysis reveal the regions which are likely involved in dual ligand binding. Further analysis of docking of FnBP_A fg‐binding region and fn N‐terminal modules suggests that if the latter binds to the fg‐binding region of FnBP_A, it would inhibit the subsequent binding of fg because of steric hindrance. The sequence analysis further suggests that the abundance of disorder promoting residue glutamic acid and dual personality (both order/disorder promoting) residue threonine in tandem repeats of FnBP_A and B proteins possibly would help the molecule to undergo a conformational change while binding with fn by β‐zipper mechanism. The segment‐based power spectral analysis was carried out which helps to understand the distribution of hydrophobic residues along the sequence particularly in intrinsic disordered tandem repeats. The results presented here will help to understand the role of internal repeats and intrinsic disorder in the molecular recognition process of a pathogenic cell surface protein.     

Antioxidant DL-alpha lipoic acid as an attenuator of adriamycin induced hepatotoxicity in rat model

Protective efficacy of DL-alpha lipoic acid on adriamycin induced hepatotoxicity was evaluated in rats. Adriamycin toxicity, induced by a single injection (ip; 15 mg/kg body wt), was expressed by an elevation in alanine transaminase, aspartate transaminase, bilirubin levels in serum and alkaline phosphatase, lactate dehydrogenase, alanine transaminase, aspartate transaminase activity in hepatic tissue. Adriamycin produced significant increase in malondialdehyde levels indicating tissue lipid peroxidation and potentially inhibiting the activity of antioxidant, reduced glutathione and antioxidant enzymes, catalase, superoxide dismutase, glutathione peroxidase, glutathione reductase, glutathione-S-transferase, glucose-6-phosphate dehydrogenase. The present results showed that pretreatment with lipoic acid [75 mg/kg body wt/day (ip), 24 h prior to administration of adriamycin] significantly restored various cellular activity suggesting the antioxidant potential of lipoic acid in ameliorating the hepatotoxicity induced by adriamycin.     

Solubilization of insoluble zinc compounds by Gluconacetobacter diazotrophicus and the detrimental action of zinc ion (Zn2+) and zinc chelates on root knot nematode Meloidogyne incognita

AIM: To examine the zinc (Zn) solubilization potential and nematicidal properties of Gluconacetobacter diazotrophicus. METHODS AND RESults: Atomic Absorption Spectrophotometer, Differential Pulse Polarography and Gas Chromatography Coupled Mass Spectrometry were used to estimate the total Zn and Zn(2+) ions and identify the organic acids present in the culture supernatants. The effect of culture filtrate of Zn-amended G. diazotrophicus PAl5 on Meloidogyne incognita in tomato was examined under gnotobiotic conditions. Gluconacetobacter diazotrophicus PAl5 effectively solubilized the Zn compounds tested and 5-ketogluconic acid was identified as the major organic acid aiding the solubilization of zinc oxide. The presence of Zn compounds in the culture filtrates of G. diazotrophicus enhanced the mortality and reduced the root penetration of M. incognita under in vitro conditions. CONCLUSIONS: 5-ketogluconic acid produced by G. diazotrophicus mediated the solubilization process and the available Zn(2+) ions enhanced the nematicidal activity of G. diazotrophicus against M. incognita. SIGNIFICANCE AND IMPACT OF THE STUDY: Zn solubilization and enhanced nematicidal activity of Zn-amended G. diazotrophicus provides the possibility of exploiting it as a plant growth promoting bacteria.     

Development and Utilization of VHH Antibodies Derived from Camelus Dromedarius Against Foot-and-Mouth Disease Virus

Foot-and-mouth disease (FMD) is an acute, highly contagious, and economically devastating viral disease of domestic and wildlife species. For effective implementation of FMD control program, there is an imperative need for developing a rapid, sensitive, and specific diagnostics which help in the identification of serotypes involved in the outbreaks. The humoral immune response of the Camelidae is unique since in these animals 75% of circulating antibodies are constituted by heavy-chain antibodies and 25% are conventional immunoglobulin with two identical heavy chains. In the present study, we developed and characterized FMD virus-specific single-domain heavy-chain antibodies (VHHs) against inactivated whole-virus antigens of FMDV serotypes O (INDR2/1975), A (IND40/2000), and Asia 1 (IND63/1972) vaccine strains. After six rounds of panning and enrichment, these VHHs were stably expressed in Escherichia coli cells. The VHHs directed against outer capsid proteins of FMD virus were successfully utilized as the capture antibody in liquid-phase blocking ELISA (LPBE) thus replacing rabbit coating antibodies. Our study demonstrated the utility of FMD virus-specific VHHs as potential candidates in FMD research and diagnostic application.     

Neutrophil Recruitment to Lymph Nodes Limits Local Humoral Response to Staphylococcus aureus

Neutrophils form the first line of host defense against bacterial pathogens. They are rapidly mobilized to sites of infection where they help marshal host defenses and remove bacteria by phagocytosis. While splenic neutrophils promote marginal zone B cell antibody production in response to administered T cell independent antigens, whether neutrophils shape humoral immunity in other lymphoid organs is controversial. Here we investigate the neutrophil influx following the local injection of Staphylococcus aureus adjacent to the inguinal lymph node and determine neutrophil impact on the lymph node humoral response. Using intravital microscopy we show that local immunization or infection recruits neutrophils from the blood to lymph nodes in waves. The second wave occurs temporally with neutrophils mobilized from the bone marrow. Within lymph nodes neutrophils infiltrate the medulla and interfollicular areas, but avoid crossing follicle borders. In vivo neutrophils form transient and long-lived interactions with B cells and plasma cells, and their depletion augments production of antigen-specific IgG and IgM in the lymph node. In vitro activated neutrophils establish synapse- and nanotube-like interactions with B cells and reduce B cell IgM production in a TGF- β1 dependent manner. Our data reveal that neutrophils mobilized from the bone marrow in response to a local bacterial challenge dampen the early humoral response in the lymph node.