Girish Kulkarni

Natural yeast flora of different varieties of grapes used for wine making in India

The natural Saccharomyces and non-Saccharomyces yeast flora present on the grape berries significantly affect wine production. Six grape varieties, Bangalore blue, Zinfandel, Cabernet, Chenin Blanc, Sauvignon Blanc and Shiraz are being used in India for wine making. The yeast diversity was studied on the basis of morphological, colony, physiological characteristics and 5.8S-ITS sequencing of rDNA of the isolates. Eleven different species belonging to seven genera were identified as: Candida azyma, Candida quercitrusa, Debaryomyces hansenii, Hanseniaspora guilliermondii, Hanseniaspora viniae, Hanseniaspora uvarum, Issatchenkia orientalis, Issatchenkia terricola, Pichia membranifaciens, Saccharomyces cerevisiae and Zygoascus steatolyticus. H. guilliermondii was the predominant species while S. cerevisiae was observed occasionally in the six vine varieties. For the first time, C. azyma was isolated from Bangalore blue and Cabernet varieties grown in different localities. This association may be attributed to the change in cropping pattern from sugarcane to viticulture in the vine growing regions and the known association of C. azyma with sugarcane phylloplane. Further analysis of the indigenous strains and the qualitative and quantitative changes in the flora during fermentation will be useful to understand wine quality and to design preservation strategies to control wine spoilage.

Characterization and identification of Geobacillus spp. isolated from Soldhar hot spring site of Garhwal Himalaya, India.

13 morphologically distinct strains of thermophilic bacteria isolated from a hot spring site in Garhwal region of Indian Himalaya have been characterized and identified using phenotypic and genotypic characters. All the strains developed circular to irregular colonies between 2–3 mm on Tryptone Yeast extract (TY) agar plates at 65 °C following 24–36 h incubation. In TY broth, facultative bacterial growth was observed within 12–16 h of incubation at 65 °C. The bacterial strains could tolerate a temperature range between 40–45 °C to 85–90 °C (optimum 65–70 °C) and pH between 4–11 (optimum 6–8). The cell morphology varied from short to long rods arranged in single, diplobacilli (in V or L shape) or short or long spiral chains with coiling. The bacterial strains varied in respect of their biochemical tests conducted for various enzymes, fermentation of sugars, tolerance to antibiotics and salt. Based on the 16S rRNA analysis, 11 strains showed maximum similarity with Geobacillus stereothermophilus, one strain with G. kaustophilus and one with Geobacillus sp. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Midgut Microbial Community of Culex quinquefasciatus Mosquito Populations from India

The mosquito Culex quinquefasciatus is a ubiquitous species that serves as a major vector for west nile virus and lymphatic filariasis. Ingestion of bloodmeal by females triggers a series of physiological processes in the midgut and also exposes them to infection by these pathogens. The bacteria normally harbored in the midgut are known to influence physiology and can also alter the response to various pathogens. The midgut bacteria in female Cx. quinquefasciatus mosquitoes collected over a large geographical area from India was studied. Examination of 16S ribosomal DNA amplicons from culturable microflora revealed the presence of 83 bacterial species belonging to 31 bacterial genera. All of these species belong to three phyla i.e. Proteobacteria, Firmicutes and Actinobacteria. Phylum Proteobacteria was the most dominant phylum (37 species), followed by Firmicutes (33 species) and Actinobacteria (13 species). Phylum Proteobacteria, was dominated by members of γ-proteobacteria class. The genus Staphylococcus was the largest genus represented by 11 species whereas Enterobacter was the most prevalent genus and recovered from all the field stations except Leh. Highest bacterial prevalence was observed from Bhuj (22 species) followed by Nagrota (18 species), Masimpur (18 species) and Hathigarh (16 species). Whereas, least species were observed from Leh (8 species). It has been observed that individual mosquito harbor extremely diverse gut bacteria and have very small overlap bacterial taxa in their gut. This variation in midgut microbiota may be one of the factors responsible for variation in disease transmission rates or vector competence within mosquito population. The present data strongly encourage further investigations to verify the potential role of the detected bacteria in mosquito for the transmission of lymphatic filariasis and west nile virus. To the best of our knowledge this is the first study on midgut microbiota of wild Cx. quinquefasciatus from over a large geographical area.

Bacterial diversity in different regions of gastrointestinal tract of Giant African Snail (Achatina fulica)

The gastrointestinal (GI) tract of invasive land snail Achatina fulica is known to harbor metabolically active bacterial communities. In this study, we assessed the bacterial diversity in the different regions of GI tract of Giant African snail, A. fulica by culture‐independent and culture‐dependent methods. Five 16S rRNA gene libraries from different regions of GI tract of active snails indicated that sequences affiliated to phylum γ‐Proteobacteria dominated the esophagus, crop, intestine, and rectum libraries, whereas sequences affiliated to Tenericutes dominated the stomach library. On phylogenetic analysis, 30, 27, 9, 27, and 25 operational taxonomic units (OTUs) from esophagus, crop, stomach, intestine, and rectum libraries were identified, respectively. Estimations of the total bacterial diversity covered along with environmental cluster analysis showed highest bacterial diversity in the esophagus and lowest in the stomach. Thirty‐three distinct bacterial isolates were obtained, which belonged to 12 genera of two major bacterial phyla namely γ‐Proteobacteria and Firmicutes. Among these, Lactococcus lactis and Kurthia gibsonii were the dominant bacteria present in all GI tract regions. Quantitative real‐time polymerase chain reaction (qPCR) analysis indicated significant differences in bacterial load in different GI tract regions of active and estivating snails. The difference in the bacterial load between the intestines of active and estivating snail was maximum. Principal component analysis (PCA) of terminal restriction fragment length polymorphism suggested that bacterial community structure changes only in intestine when snail enters estivation state.

Effect of repeated in vitro sub-culturing on the virulence of Metarhizium anisopliae against Helicoverpa armigera (Lepidoptera: Noctuidae)

Abstract The effect of repeated conidial sub-culturing of Metarhizium anisopliae on its virulence against Helicoverpa armigera (Hübner) was studied. The LT50 observed against third instar larvae of H. armigera for the first sub-culture was 3.4 days; it increased to 4.5 and 5.6 days for the 20th and the 40th sub-cultures, respectively. The LT50 values after passage of the 40th sub-culture on H. armigera decreased to 4.4 and 3.7 days for the 40th (first in vivo) and the 40th (fifth in vivo) passages, respectively. Similarly, the LC50 of M. anisopliae towards third instar larvae of H. armigera increased from the first sub-culture (0.17×104) to (3.0×104) for the 40th conidial transfers on potato dextrose agar and again decreased to 0.74×104 and 0.23×104 in the 40th (first in vivo) and the 40th (fifth in vivo) passage, respectively. Similar trends for LC50 and LT50 values were seen when sugarcane woolly aphid, Ceratovacuna lanigera Zehntner was used as a host. Significant variation in appressorium formation and cuticle-degrading enzyme production such as chitinase, chitin deacetylase, chitosanase and protease during subsequent sub-culturing and passage through H. armigera was observed. Though there was no effect on internal transcribed spacer (ITS) sequence pattern, interestingly, in randomly amplified polymorphic DNA (RAPD), significant differences in the band intensities and in the banding pattern for different sub-cultures of M. anisopliae were observed. As stable virulence towards the insect pest is desirable for commercialisation of a mycoinsecticide, such changes in virulence due to repeated in vitro transfer need to be monitored and minimised.

Comparison of Metarhizium isolates for biocontrol of Helicoverpa armigera (Lepidoptera: Noctuidae) in chickpea

Abstract Metarhizium isolates from soil (53) and insect hosts (10) were evaluated for extracellular production of cuticle degrading enzyme (CDE) activities such as chitinase, chitin deacetylase (CDA), chitosanase, protease and lipase. Regression analysis demonstrated the relation of CDE activities with Helicoverpa armigera mortality. On basis of this relation, ten isolates were selected for further evaluation. Subsequently, based on LT50 of the 10 isolates towards H. armigera, five isolates were selected. Out of these five isolates, three were selected on the basis of higher conidia production (60–75 g/kg rice), faster sedimentation time (ST50) (2.3–2.65 h in 0.1% (w/v) Tween 80) and lower LC50 (1.4–5.7×103 conidia/mL) against H. armigera. Finally, three Metarhizium isolates were selected for the molecular fingerprinting using ITS sequencing and RAPD patterning. All three isolates, M34412, M34311 and M81123, showed comparable RAPD patterns with a 935G primer. These were further evaluated for their field performance against H. armigera in a chickpea crop. The percent efficacies with the three Metarhizium isolates were from 65 to 72%, which was comparable to the chemical insecticide, endosulfan (74%).

Technicalities and Glitches of Terminal Restriction Fragment Length Polymorphism (T-RFLP)

Terminal restriction fragment length polymorphism (T-RFLP) is a rapid, robust, inexpensive and simple tool for microbial community profiling. Methods used for DNA extraction, PCR amplification and digestion of amplified products have a considerable impact on the results of T-RFLP. Pitfalls of the method skew the similarity analysis and compromise its high throughput ability. Despite a high throughput method of data generation, data analysis is still in its infancy and needs more attention. Current article highlights the limitations of the methods used for data generation and analysis. It also provides an overview of the recent methodological developments in T-RFLP which will assist the readers in obtaining real and authentic profiles of the microbial communities under consideration while eluding the inherent biases and technical difficulties.

Generation, annotation, and analysis of ESTs from midgut tissue of adult female Anopheles stephensi mosquitoes

BackgroundMalaria is a tropical disease caused by protozoan parasite, Plasmodium, which is transmitted to humans by various species of female anopheline mosquitoes. Anopheles stephensi is one such major malaria vector in urban parts of the Indian subcontinent. Unlike Anopheles gambiae, an African malaria vector, transcriptome of A. stephensi midgut tissue is less explored. We have therefore carried out generation, annotation, and analysis of expressed sequence tags from sugar-fed and Plasmodium yoelii infected blood-fed (post 24 h) adult female A. stephensi midgut tissue.ResultsWe obtained 7061 and 8306 ESTs from the sugar-fed and P. yoelii infected mosquito midgut tissue libraries, respectively. ESTs from the combined dataset formed 1319 contigs and 2627 singlets, totaling to 3946 unique transcripts. Putative functions were assigned to 1615 (40.9%) transcripts using BLASTX against UniProtKB database. Amongst unannotated transcripts, we identified 1513 putative novel transcripts and 818 potential untranslated regions (UTRs). Statistical comparison of annotated and unannotated ESTs from the two libraries identified 119 differentially regulated genes. Out of 3946 unique transcripts, only 1387 transcripts were mapped on the A. gambiae genome. These also included 189 novel transcripts, which were mapped to the unannotated regions of the genome. The EST data is available as ESTDB at http://mycompdb.bioinfo-portal.cdac.in/cgi-bin/est/index.cgi.Conclusion3946 unique transcripts were successfully identified from the adult female A. stephensi midgut tissue. These data can be used for microarray development for better understanding of vector-parasite relationship and to study differences or similarities with other malaria vectors. Mapping of putative novel transcripts from A. stephensi on the A. gambiae genome proved fruitful in identification and annotation of several genes. Failure of some novel transcripts to map on the A. gambiae genome indicates existence of substantial genomic dissimilarities between these two potent malaria vectors.

Draft genome of Ochrobactrum intermedium strain M86 isolated from non-ulcer dyspeptic individual from India

BackgroundOchrobactrum intermedium is an emerging opportunistic pathogen of humans that is closely related to members of the genus Brucella. Earlier, we reported the case of an Indian subject with non-ulcer dyspeptic symptoms whose urease positive gastric biopsy revealed the presence of Helicobacter pylori along with non-Helicobacter like bacteria, eventually cultured and identified as O. intermedium strain M86.ResultsHere, we describe the unclosed draft genome of the strain M86 with a length of 5,188,688 bp and mean G+C content of 57.9%. We have also identified many putative gene clusters that might be responsible for its persistence in the gastric mucosa.Comparative analysis of genomic features of Ochrobactrum intermedium strain M86 and Ochrobactrum intermedium LMG 3301T was also done.ConclusionsThis paper attempts to gain whole-genome based insights into the putative gene determinants of O. intermedium for survival in the highly acidic stomach lumen environment .Identification of genes putatively involved in the various metabolic pathways may lead to a better understanding of the survival of O. intermdedium in acidic condition.

Molecular phylogenetic study of Culex quinquefasciatus mosquito from different geographical regions of India using 16S rRNA gene sequences.

Culex quinquefasciatus is a major vector of filariasis and various encephalitis in India and worldwide. Vector control remains the most successful strategy for the suppression of mosquito borne diseases. The genetic structure of vector populations in terms of insecticide resistance and susceptibility or refractoriness to infection may possibly vary. To exploit the genetic variability in vector population could pave the path for the alternative strategies in vector management. The sequences of ribosomal RNA molecules have been widely used for such studies. Here, we examined the molecular phylogenetic relationship among the Cx. quinquefasciatus collected from different geographical regions of India, using 16S ribosomal RNA (16S rRNA) gene nucleotide sequences. The distances among the species were measured using Pearson correlation; the Neighbor-Joining (NJ) method was used for the clustering with appropriate bootstrap values using Data Analysis in Molecular Biology and Evolution (DAMBE) software. The results revealed that the populations are genetically diverse. Based on the distance values and the tree topology on the basis of 16S rRNA sequences reflected the clear biogeographical and geoclimatic pattern among the different geographical populations from India.