Energy generation from bioelectrochemical techniques: Concepts, reactor configurations and modeling approaches

The process industries play a significant role in boosting the economy of any nation. However, poor management in several industries has been posing worrisome threats to an environment that was previously immaculate. As a result, the untreated waste and wastewater discarded by many industries contain abundant organic matter and other toxic chemicals. It is more likely that they disrupt the proper functioning of the water bodies by perturbing the sustenance of many species of flora and fauna occupying the different trophic levels. The simultaneous threats to human health and the environment, as well as the global energy problem, have encouraged a number of nations to work on the development of renewable energy sources. Hence, bioelectrochemical systems (BESs) have attracted the attention of several stakeholders throughout the world on many counts. The bioelectricity generated from BESs has been recognized as a clean fuel. Besides, this technology has advantages such as the direct conversion of substrate to electricity, and efficient operation at ambient and even low temperatures. An overview of the BESs, its important operating parameters, bioremediation of industrial waste and wastewaters, biodegradation kinetics, and artificial neural network (ANN) modeling to describe substrate removal/elimination and energy production of the BESs are discussed. When considering the potential for use in the industrial sector, certain technical issues of BES design and the principal microorganisms/biocatalysts involved in the degradation of waste are also highlighted in this review.

Electric field modulated peptide based hydrogel nanocatalysts

The ability to modulate self-assembly is the key to manufacture application-oriented materials. In this study, we investigated the effect of three independent variables that can modulate the catalytic activity of self-assembling peptides. The first two variables, amino acid sequence and its stereochemistry, were examined for their specific roles in the epitaxial growth and hydrogelation properties of a series of catalytic tripeptides. We observed that aromatic π-π interactions that direct the self-assembly of designed peptides, and the catalytic properties of hydrogels, are governed by the position and chirality of the proline residue. Subsequently, the influence of the third variable, an external electric field, was also tested to confirm its catalytic efficiency for the asymmetric C-C bond-forming aldol reaction. In particular, the electric field treated pff and PFF gels showed 10 and 36% higher stereoselectivity, respectively, compared with the control. Structure-property analysis using CD and FTIR spectroscopy indicates the electric field-induced beta to non-beta conformational transition in the peptide secondary structure, which corroborates with its reduced cross-link density and fibril width, respectively. Amplitude sweep rheology of the gels suggests a decrease in the storage modulus, with increased field strength. The results showed that an electric field of optimal strength can modulate the physical characteristics of the hydrogel, which in turn is manifested in the observed difference in enantioselectivity.

Human intervertebral discs harbour a unique microbiome and dysbiosis determines health and disease

BACKGROUND

To document the role of sub-clinical infections in disc disorders and investigate the existence of microbiome in intervertebral discs (IVD).

METHODS

Genomic DNA from 24 lumbar IVDs [8-MRI normal discs (ND) from brain dead yet alive organ donors, 8-disc herniation (DH), 8-disc degeneration (DD)] was subjected to 16SrRNA sequencing for profiling the diversity of human disc microbiome in health and disease. The disc microbiome was further compared to established human gut and skin microbiomes.

RESULTS

All healthy MRI normal discs from brain dead yet alive organ donors also had a rich bacterial presence. A total of 424 different species (355-ND, 346-DD, and 322-DH) were detected, with 42.75% OTUs being classified at kingdom level, 44% at the phylum level, 22.62% at genus level, and 5.5% at species level. Varying biodiversity and abundance between healthy and diseased discs were documented with protective bacteria being abundant in normal discs, and putative pathogens abundant in DD and DH. Propionibacterium acnes had a similar but lower abundance to other pathogens in all three groups ND (3.07%), DD (3.88%), DH (1.56%). Fifty-eight bacteria were common between gut and IVD microbiomes, 29 between skin and IVD microbiomes, and six common to gut/skin/IVD.

CONCLUSION

Our study challenges the hitherto concept of sterility in healthy IVD and documented a microbiome even in MRI normal healthy discs. The varying abundance of bacteria between ND, DD, and DH documents 'dysbiosis' as a possible etiology of DD. Many known pathogens were identified in greater abundance than Propionibacterium acnes, and there was evidence for the presence of the gut/skin/spine microbiome axis.

Proteomic Signature of Nucleus Pulposus in Fetal Intervertebral Disc

Study Design

Profiling proteins expressed in the nucleus pulposus of fetal intervertebral disc (IVD).

Purpose

To evaluate the molecular complexity of fetal IVDs not exposed to mechanical, traumatic, inflammatory, or infective insults to generate improved knowledge on disc homeostasis.

Overview of Literature

Low back pain is the most common musculoskeletal disorder, causing a significant reduction in the quality of life, and degenerative disc disorders mainly contribute to the increasing socioeconomic burden. Despite extensive research, the causative pathomechanisms behind degenerative disc disorders are poorly understood. Precise molecular studies on the intricate biological processes involved in maintaining normal disc homeostasis are needed.

Methods

IVDs of nine fetal specimens obtained from medical abortions were used to dissect out the annulus fibrosus and nucleus pulposus under sterile operating conditions. Dissected tissues were transferred to sterile Cryovials and snap frozen in liquid nitrogen before transporting to the research laboratory for protein extraction and further liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis. Collected data were further analyzed using Gene Functional Classification Tool in DAVID and STRING databases.

Results

A total of 1,316 proteins were identified through LC-MS/MS analysis of nine fetal IVD tissues. Approximately 247 proteins present in at least four fetal discs were subjected to further bioinformatic analysis. The following 10 clusters of proteins were identified: collagens, ribosomal proteins, small leucine-rich proteins, matrilin and thrombospondin, annexins, protein disulfide isomerase family proteins and peroxiredoxins, tubulins, histones, hemoglobin, and prolyl 4-hydroxylase family proteins.

Conclusions

This study provides fundamental information on the proteome networks involved in the growth and development of healthy fetal discs in humans. Systematic cataloging of proteins involved in various structural and regulatory processes has been performed. Proteins expressed most abundantly (collagen type XIV alpha 1 chain, biglycan, matrilin 1, and thrombospondin 1) in their respective clusters also elucidate the possibility of utilizing these proteins for potential regenerative therapies.

Inflammaging determines health and disease in lumbar discs-evidence from differing proteomic signatures of healthy, aging, and degenerating discs

BACKGROUND CONTEXT

The true understanding of aging and disc degeneration (DD) is still elusive. MRI has not helped our attempts to understand the health and disease status of the discs as it reflects mainly the end morphologic changes and not the changes at a molecular level. Understanding degeneration at a molecular level through proteomics might allow differentiation from normal aging and also aid in the development of biomarkers for early diagnosis and preventive therapies.

PURPOSE

To utilize proteomics to understand the molecular basis of healthy, aging, and degenerating discs and conclusively differentiate normal aging and degeneration.

STUDY DESIGN

Proteomic analysis of human intervertebral disc samples.

METHODS

L4-L5 disc samples from three groups were acquired and subjected to proteomic analysis. Samples from individuals aged in the second, third, and fourth decades were used to represent young healthy discs (Group A). Those from MRI normal donors aged in the fifth, sixth, and seventh decades represented normal aging (Group B). Five degenerated discs obtained from patients at surgery represented degeneration (Group C). The entire proteome map and alteration in protein expressions were further analyzed using bioinformatics analysis. This was a self-funded project.

RESULTS

There were 84 common proteins. Specific proteins numbered 225 in A, 315 in B, and 283 in C. By gene ontology biological process identification, Group A predominated with extracellular matrix organization, cytoskeletal structural and normal metabolic proteins. Group B differed in having additional basal expression of immune response, complement inhibitors, and senescence proteins. Group C was different, with upregulation of proteins associated with oxidative stress response, positive regulators of apoptosis, innate immune response, complement activation and defense response to gram positive bacteria indicating ongoing inflammaging.

CONCLUSIONS

Our study documented diverse proteome signatures between the young, aging and degenerating discs. Inflammaging was the main differentiator between normal biological aging and DD.

CLINICAL SIGNIFICANCE

Multiple inflammatory molecules unique to DD were identified, allowing the possibility of developing specific biomarkers for early diagnosis and thereby provide evidence-based metrics for preventive measures rather than surgical intervention and also to monitor progress of the disease.

Implementation of artificial neural network model for continuous hydrogen production using confectionery wastewater

In the present study, an artificial neural network (ANN) was implemented to estimate the hydrogen production from confectionery wastewater. From the experimental investigation, it could be concluded that maximum COD removal efficiency of 99% and hydrogen production rate of 6570 mL/d was achieved at 7.00 kg COD/m³d and 24 h HRT. To validate this, a back propagation ANN configuration of 4-12-4-2 was opted. The modelling was performed using the input parameters like time, influent chemical oxygen demand (COD), effluent pH and volatile fatty acids (VFA). The correlation coefficient between the experimental and predicted hydrogen production rate was 0.996. The result of the tested data for hydrogen production rate was successful. The calculated average percentage error (APE) for hydrogen production rate was 0.0004. As the APE values were closer to zero, the trained ANN model fitted well with the experimental data.

ISSLS PRIZE IN CLINICAL SCIENCE 2017: Is infection the possible initiator of disc disease? An insight from proteomic analysis

STUDY DESIGN

Proteomic and 16S rDNA analysis of disc tissues obtained in vivo.

OBJECTIVE

To address the controversy of infection as an aetiology for disc disorders through protein profiling. There is raging controversy over the presence of bacteria in human lumbar discs in vivo, and if they represent contamination or infection. Proteomics can provide valuable insight by identifying proteins signifying bacterial presence and, also host defence response proteins (HDRPs), which will confirm infection.

METHODS

22 discs (15-disc herniations (DH), 5-degenerate (DD), 2-normal in MRI (NM) were harvested intraoperatively and immediately snap frozen. Samples were pooled into three groups and proteins extracted were analysed with liquid chromatography-tandem mass spectrometry (LC-MS/MS). Post identification, data analysis was performed using Uniprotdb, Pantherdb, Proteome discoverer and STRING network. Authentication for bacterial presence was performed by PCR amplification of 16S rDNA.

RESULTS

LC-MS/MS analysis using Orbitrap showed 1103 proteins in DH group, compared to 394 in NM and 564 in DD. 73 bacterial specific proteins were identified (56 specific for Propionibacterium acnes; 17 for Staphylococcus epidermidis). In addition, 67 infection-specific HDRPs, unique or upregulated, such as Defensin, Lysozyme, Dermcidin, Cathepsin-G, Prolactin-Induced Protein, and Phospholipase-A2, were identified confirming presence of infection. Species-specific primers for P. acnes exhibited amplicons at 946 bp (16S rDNA) and 515 bp (Lipase) confirming presence of P. acnes in both NM discs, 11 of 15 DH discs, and all five DD discs. Bioinformatic search for protein-protein interactions (STRING) documented 169 proteins with close interactions (protein clustering co-efficient 0.7) between host response and degenerative proteins implying that infection may initiate degradation through Ubiquitin C.

CONCLUSION

Our study demonstrates bacterial specific proteins and host defence proteins to infection which strengthen the hypothesis of infection as a possible initiator of disc disease. These results can lead to a paradigm shift in our understanding and management of disc disorders.

FTIR Study of Molecular Interaction in Butyl Methacrylate–Organic Solvents Mixtures

FTIR spectroscopic study of butyl methacrylate (BMA) in different pure organic solvents were undertaken to investigate the solute–solvent interactions. The frequency of carbonyl stretching vibration ν(C=O) of BMA is correlated with the solvent properties such as the KBM parameter, the solvent acceptor number (AN), and the linear salvation energy relationships (LSER). The solvent-induced stretching vibration frequency shifts showed a better correlation with LSER parameters than AN. While no linear correlation between dielectric constants and the frequencies showed that the KBM relationship was unsuitable for this molecule. Also the solvent effect on the strength of hydrogen bond formation between free OH group of 1-butanol and C=O group of BMA is discussed in terms of local specific interaction between the solute and solvent.

Dielectric Relaxation Studies of Primary Alcohols and Alkyl Methacrylates

Dielectric relaxation studies of alkyl (methyl, ethyl, and butyl) methacrylates with primary alcohols (1-propanol, 1-pentanol, 1-heptanol, and 1-octanol) at 9.84 GHz have been studied in benzene at 298 K. The results show that the most likely association between alcohol and ester is 1 : 1 complex through the free hydroxyl group of the alcohol and the carbonyl group of ester and the alkyl chain-length of both the alcohols and esters plays an important role in the determination of the strength of hydrogen bond (O–H:O=C) formed. Comparative study of free energy of activation for the dielectric relaxation and viscous flow suggest the fact that the process of viscous flow involves greater interference by neighbors than does dielectric relaxation, as the latter takes place by rotation only whereas the viscous flow involves both the rotational and translational forms of motion.

Molecular interactions in alcohol-ethyl methacrylate mixtures

Molecular interaction between alcohols (1-propanol, 1-butanol, s-butanol, t-butanol, 1-pentanol, 1-heptanol, 1-octanol and 1-decanol) with ethyl methacrylate has been studied in n-heptane, CCl(4) and benzene at 298K using FTIR spectroscopic and dielectric methods. The result obtained from both the methods indicates only the existence of most likely 1:1 complex formation between the alcohol and ethyl methacrylate in these systems. The alkyl chain length of alcohol and the solvent used play a significant role in the strength of hydrogen bond (O-H:O=C) determined on the basis of spectral and dielectric parameters.

Hydrogen bonding interaction between acrylic esters and monohydric alcohols in non-polar solvents: An FTIR study

The association between acrylic esters (methyl methacrylate, ethyl methacrylate and butyl methacrylate) and some monohydric (primary, secondary and tertiary) alcohols in non-polar solvents, viz. n-heptane, CCl4 and benzene has been investigated by means of FTIR spectroscopy. The most likely association complex between alcohol and acrylic ester is 1:1 stoichiometric complex through the hydroxyl group of alcohol and the carbonyl group of acrylic ester. The formation constant of the 1:1 complexes has been calculated using Nash method. It appears that the primary alcohols have larger formation constant than the secondary and tertiary alcohols. The results show that the proton donating power of the alcohols decreases in the order primary>secondary>tertiary and the association constant increases with the increase in carbon chain of the alkyl group of acrylic esters and alcohols. Also the results show a significant dependence of the association constant upon the solvents used. The solvent effect on the formation of hydrogen bond equilibria is discussed in terms of specific interaction between the solute and solvent.

Molecular interaction studies of acrylic esters with 1-alcohols

Hydrogen bonding between 1-alcohols and acrylic esters in n-heptane has been studied by FTIR spectroscopic method. The formation constant of the 1:1 complexes has been calculated using Nash method. The values of formation constant and free energy change vary with alcohol and ester chain length, which suggests that the strengths of the intermolecular O-H...O=C bonds are shown to be dependent on the alkyl group of acrylic esters and the 1-alcohols and the results shows that the proton donating ability of 1-alcohols is in the order: 1-propanol<1-butanol<1-pentanol and the accepting ability of acrylic esters is in the order: methyl methacrylate<ethyl methacrylate<butyl methacrylate.

Mycobacterial lipoarabinomannans modulate cytokine production in human T helper cells by interfering with raft/microdomain signalling

Lipoarabinomannans (LAMs) are major lipoglycans of the mycobacterial envelope and constitute immunodominant epitopes of mycobacteria. In this paper, we show that mannose-capped (ManLAM) and non-mannose-capped (PILAM) mycobacterial lipoglycans insert into T helper cell rafts without apparent binding to known receptors. T helper cells modified by the insertion of PILAM responded to CD3 cross-linking by decreasing type 1 (IL-2 and IFN-gamma) and increasing type 2 (IL-4 and IL-5) cytokine production. Modification by the mannose-capped ManLAMs had similar, but more limited effects on T helper cell cytokine production. When incorporated into isolated rafts, PILAMs modulated membrane-associated kinases in a dose-dependent manner, inducing increased phosphorylation of Src kinases and Cbp/PAG in Th1 rafts, while decreasing phosphorylation of the same proteins in Th2 rafts. Mycobacterial lipoglycans thus modify the signalling machineries of rafts/microdomains in T helper cells, a modification of the membrane organization that eventually leads to an overall enhancement of type 2 and inhibition of type 1 cytokine production.

Role of Keratinocytes in Antigen Presentation and Polarization of Human T Lymphocytes

Allergic contact dermatitis is a T-cell-mediated inflammatory skin disease in which interaction between skin keratinocytes and migrating T lymphocytes may play a critical part. In this study, the role of keratinocytes as allergen-/antigen-presenting cells (APCs) leading to activation of T lymphocytes is investigated using a human epidermal cell line A431. It is known that cultured cells do not express human leucocyte antigen (HLA) and hence can be used as APCs independent of HLA profile of both APCs and T cells from human volunteers. This cell line responded to common allergens and irritants by inducing or upregulating the cell-surface expression of HLA-DR, and intercellular adhesion molecule-1 and B7 mRNA transcripts in keratinocytes. In addition, allergen-primed A431 cells also induced allergen-specific proliferation of human T lymphocytes in cocultures. Anti-HLA-DR, interleukin-1alpha (IL-1alpha) antibodies and lysosomotropic agent chloroquine inhibited the proliferation. Allergens also upregulated cytokines IL-1alpha, granulocyte-macrophage colony-stimulating factor, Gro-alpha and IL-12 in keratinocytes. Further, keratinocytes activated by allergens induced polarization of activated T lymphocytes to the Th1 phenotype.

A novel extracellular protein of Streptomyces peucetius binds to daunorubicin but does not inhibit the bioactivity of the antibiotic

Extracellular proteins of Streptomyces peucetius that bind to a red pigment were identified during the course of isolation of mutants defective in daunorubicin production. Two pigment-protein complexes were partially purified and this complex inhibited the growth of Bacillus subtilis. Routine solvent extraction could not separate the pigment from purified pigment-protein complex. Treatment with 2% SDS at 100 degrees C followed by solvent extraction also failed to separate the protein from the pigment. However, the pigment could be separated from the purified pigment-protein complex by heating it in 0.1M HCl at 100 degrees C followed by solvent extraction. The pigment extracted from the complex was analyzed by HPLC and found to be daunorubicin.

Large-restriction-fragment polymorphism analysis of Mycobacterium chelonae and Mycobacterium terrae isolates

Mycobacterium chelonae and Mycobacterium terrae were reported to be frequently present in the environment of the Mycobacterium bovis BCG trial area in south India. Six isolates of M. chelonae and four isolates of M. terrae obtained from different sources in this area were analyzed by pulsed-field gel electrophoresis (PFGE) to examine large-restriction-fragment (LRF) polymorphism using the chromosomal DNA digested with DraI and XbaI restriction enzymes. With the exception of one isolate of M. terrae, DNA from all other isolates could be digested with DraI and XbaI and resulted in separable fragments. Visual comparison of the LRFs showed a unique pattern for each of the isolates tested. A computer-assisted dendrogram of the percent similarity demonstrated a high degree of genetic diversity in this group of isolates. This study demonstrates that species of nontuberculous mycobacteria, particularly M. chelonae and M. terrae, can be successfully typed by their LRF pattern using PFGE, which does not require species-specific DNA probes.

Cytokine profiles in paraffin-embedded biopsy samples of lepromatous leprosy patients: semi-quantitative measure of cytokine mRNA using RT-PCR

A reproducible technique for fixation of tissue, RNA extraction and reverse transcription polymerase chain reaction (RT-PCR) analysis from paraffin-embedded leprosy biopsies, has been developed and used to study the mRNA profiles. This approach is valuable in retrospective analysis of gene expression, and the handling of infectious biopsy material is also minimized. Among the methods of RNA extraction compared, the most efficient method was found to be incubation of the tissue sections in digestion buffer followed by extraction with Trizol. The experimental conditions were optimized for first strand cDNA synthesis and PCR, and used to measure the quantity of cytokine transcripts in biopsy materials. Interleukin-10 (IL-10) mRNA was detectable in all cases examined, which correlates well with other earlier reports using frozen tissues. However, IL-5 transcripts were present in 60% of the biopsies, unlike the earlier reports which showed IL-5 mRNA in all LL cases. Transforming growth factor-beta (TGF-beta) mRNA was detected in 80% of the biopsies, and this confirmed earlier immuno-cytochemical data which showed TGF-beta protein in all cases. Tumor necrosis factor-alpha mRNA was found in about 60% of the biopsies; whereas interferon gamma mRNA was detected in 30% of the LL cases. In conclusion, the results obtained in our study confirm and extend earlier observations which examined cytokines in peripheral blood cells and dermal lesions of leprosy. The simplicity of this method would allow the examination of a large number of samples across the spectrum of leprosy.

Isolation and characterization of stable mutants of Streptomyces peucetius defective in daunorubicin biosynthesis

Daunorubicin and its derivative doxorubicin are antitumour anthracycline antibiotics produced by Streptomyces peucetius. In this study we report isolation of stable mutants of S. peucetius blocked in different steps of the daunorubicin biosynthesis pathway. Mutants were screened on the basis of colony colour since producer strains are distinctively coloured on agar plates. Different mutants showed accumulation of aklaviketone, epsilon-rhodomycinone, maggiemycin or 13-dihydrocarminomycin in their culture filtrates. These results indicate that the mutations in these isolates affect steps catalysed by dnrE (mutants SPAK and SPMAG), dnrS (SPFS and SPRHO) and doxA (SPDHC) gene products.

Purification, cloning, and DNA sequence analysis of a chitinase from an overproducing mutant of Streptomyces peucetius defective in daunorubicin biosynthesis

Extracellular chitinases of Streptomyces peucetius and a chitinase overproducing mutant, SPVI, were purified to homogeneity by ion exchange and gel filtration chromatography. The purified enzyme has a molecular mass of 42 kDa on SDS-PAGE, and the N-terminal amino acid sequence of the protein from the wild type showed homology to catalytic domains (Domain IV) of several other Streptomyces chitinases such as S. lividans 66, S. coelicolor A3(2), S. plicatus, and S. thermoviolaceus OPC-520. Purified SPVI chitinase cross-reacted to anti-chitinase antibodies of wild-type S. peucetius chitinase. A genomic library of SPVI constructed in E. coli using lambda DASH II was probed with chiC of S. lividans 66 to screen for the chitinase gene. A 2.7 kb fragment containing the chitinase gene was subcloned from a lambda DASH II clone, and sequenced. The deduced protein had a molecular mass of 68 kDa, and showed domain organization similar to that of S. lividans 66 chiC. The N-terminal amino acid sequence of the purified S. peucetius chitinase matched with the N-terminus of the catalytic domain, indicating the proteolytic processing of 68 kDa chitinase precursor protein to 42 kDa mature chitinase containing the catalytic domain only. A putative chiR sequence of a two-component regulatory system was found upstream of the chiC sequence.

Isolation of a chitinase overproducing mutant of Streptomyces peucetius defective in daunorubicin biosynthesis

Streptomyces peucetius, producer of the antitumor anthracycline antibiotic daunorubicin, was mutagenized, and mutants defective in daunorubicin biosynthesis were screened. One mutant (SPVI), which failed to produce daunorubicin, was found to overproduce an extracellular chitinase. Time course analyses of chitinase production and of the extracellular protein profile showed that the increase in activity is due to increased synthesis of the enzyme protein. The production of chitinase in SPVI was repressed by glucose as in the case of wild-type S. peucetius. PFGE analysis of VspI restriction fragments of S. peucetius and SPVI showed that there was no major alteration in the mutant genome. The hybridization pattern of S. peucetius and SPVI genomic DNA digested with various restriction enzymes was identical when probed with dnrUVJI genes of the S. peucetius daunorubicin cluster and chiA of Streptomyces lividans 66. The possible step affected in the daunorubicin biosynthetic pathway could be a polyketide synthase, since aklanonic acid, the earliest detectable intermediate in the daunorubicin pathway, was not synthesized in SPVI.

Allele frequency distribution for the variable number of tandem repeat locus D10S28 in Tamil Nadu (south India) population

Allele frequencies were determined in unrelated individuals of Tamil speaking population from the Madras City (Tamil Nadu, South India) area for the polymorphic DNA locus D10S28 using the probe TBQ7. Membranes hybridized with the probe YNH24 were subjected to deprobing and were subsequently hybridized with random priming - labeled, purified inserts of TBQ7. The sizes of the fragments were grouped to 100 bp as well as to arbitrary fixed bins (Federal Bureau of Investigation / Royal Canadian Mounted Police). There were 14 bins in the latter with the most common bin being 11 (1789-1924 bp) with a frequency of 9.8%. We observed a heterozygosity of 92% comparable to Caucasian populations. The data presented here can be used as the basis for utilizing this variable number of tandem repeats (TNTR) DNA marker for paternity determinations and forensic investigations.

DNA profiling of the VNTR locus D2S44 in the population of Madras City and in the tribal Kotas of the Nilgiri Hills, south India

Allele frequency distribution of the VNTR locus D2S44 was studied in Tamil Nadu (South India) population. Randomly chosen individuals (Tamils of the plains, Madras City; N = 142) were tested for HaeIII-generated polymorphism detectable by probe YNH24, and the allele sizes and frequencies were determined. Heterozygosity (93.6%) observed in the Tamils is comparable to that of other populations; the size and frequency distribution of alleles, however, vary significantly. The most prevalent allele, which ranges from 1.2 to 1.9 kb, appears to be unique to the Tamil Nadu population. No mutation was observed for the D2S44 locus in family material made up by 54 subjects (N = 54) including 37 offspring. DNA polymorphism at D2S44 locus was also studied in the endogamous Kota tribe of the Nilgiri Hills, South India, using enzyme HaeIII and probe YNH24. The Kota group (N = 48) is characterized by a very high frequency (32.3%) of the bin 1197-1352 bp. The DNA profile of the Kotas shows distinct differences from that of the urban population in the plains of Tamil Nadu, South India (Tamils of Madras City). The results have also been compared with the literature available on other world populations. The outcome indicates the uniqueness of the tribal Kotas and warrants the importance of DNA profiling in other tribal, caste/endogamous groups of India. This report incidentally represents the first comprehensive DNA profiling data for the locus D2S44 from India fulfilling the requirement for forensic and other applications.

Expression of the mcrA gene of Escherichia coli is regulated posttranscriptionally, possibly by sequestration of the Shine-Dalgarno region

The polypeptides encoded by the mcrA gene were analysed using a T7 expression system. Cloned fragments of 1.6 and 1.0 kb displayed an McrA+/RglA+ phenotype and directed synthesis of a 31-kDa polypeptide. A derivative of these clones altered at an internal HindIII site displayed an McrA+/RglA- phenotype and directed production of a 23-kDa polypeptide. Smaller inserts displayed McrA-/RglA- phenotypes, though a 0.7-kb insert did direct production of a 24-kDa polypeptide. A construct carrying the 1.0-kb mcrA insert yielded a single 1.3-kb transcript. The mcrA transcript was found to start from C, G, T and G, namely the fourth, fifth, sixth and seventh nucleotides (nt), respectively, downstream from the last nt of the putative -10 region. Two mcrA transcriptional/transational fusions were made in the pT7-7 expression vector and the protein encoded by these constructs were analysed. Regulation of mcrA expression was studied by quantitative Northern analysis of RNA from various mcrA clones. Together with a computer analysis of the translation initiation region in these mRNAs, the results suggest that the expression of mcrA may be regulated at the translational level.

DNA amplification affects protease production and sporulation in Streptomyces fradiae

Chloramphenicol resistance is an unstable character in Streptomyces fradiae, since spontaneous chloramphenicol-sensitive (Cmls) mutants arose at very high frequencies. One such Cmls mutant, DM14, showed DNA amplification as well. Extracellular protease activity was tenfold higher in DM14 when compared with its wild-type parent. Protease activity decreased considerably in DM14 when treated with spectinomycin, a treatment that reduces the copy number of amplified units of DNA. Sporulation in DM14 was delayed in the presence of spectinomycin at a concentration of 5 micrograms/ml, whereas the wild type was unaffected at that concentration. The results strongly indicated that the amplified DNA affected the two secondary metabolic functions, viz., protease production and the onset of sporulation in the mutant.

Structural organization, amplification, deletion and rearrangements of DNA sequences associated with an unstable region of the chromosome of Streptomyces coelicolor A3(2)

The chromosome of Streptomyces coelicolor A3(2) carries unstable DNA sequences hybridising with DNA sequences from an unstable chromosomal region of the related species S. lividans. These S. coelicolor sequences are nearly identical to those of S. lividans TK23 in organisation but differ from those of S. lividans 66 TK64 which harbours a tandem duplication of these sequences. Southern hybridisations using heterologous probes and S. coelicolor DNA cleaved with a variety of restriction enzymes permitted us to construct a partial restriction map of the unstable region of the chromosome of S. coelicolor. Genetic analysis shows that the unstable region yields distinguishable variants with several distinct DNA rearrangements.

Nomenclature relating to restriction of modified DNA in Escherichia coli

At least three restriction systems that attack DNA containing naturally modified bases have been found in common Escherichia coli K-12 strains. These systems are McrA, McrBC, and Mrr. A brief summary of the genetic and phenotypic properties so far observed in laboratory strains is set forth, together with a proposed nomenclature for describing these properties.