Rishi Mahajan

Microbe-bio-Chemical Insight: Reviewing Interactions between Dietary Polyphenols and Gut Microbiota

OBJECTIVE Polyphenols are widespread constituents of different food commodities. These are regarded as essential micronutrients because of their well-documented health benefits. These health benefits depend on the amount of polyphenols consumed and their bioavailability in the gut. The microbial transformation of polyphenols in gut is poorly characterized, where, these polyphenols may act as promoting factors for proliferation of beneficial gut inhabitants and inhibiting the pathogenic species. CONCLUSION The aim of this review is to present a holistic view on occurrence of polyphenols, their health benefits and influence of dietary polyphenols on gut microbiota.

Characterization of cellulolytic activities of newly isolated Thelephora sowerbyi from North‐Western Himalayas on different lignocellulosic substrates

Characterization of cellulolytic activities of newly isolated Thelephora sowerbyi from North‐Western Himalayas on different lignocellulosic substrate J. Basic Microbiol. 2015, 55, 1–11 – DOI: 10.1002/jobm.201500107

Microbial diversity in an anaerobic digester with biogeographical proximity to geothermally active region

ABSTRACT Anaerobic digestion of agricultural biomass or wastes can offer renewable energy, to help meet the rise in energy demands. The performance of an anaerobic digester considerably depends upon the complex interactions between bacterial and archaeal microbiome, which is greatly influenced by environmental factors. In the present study, we evaluate a microbial community of digester located at two different geographical locations, to understand whether the biogeographical proximity of a digester to a geothermally active region has any influence on microbial composition. The comparative microbial community profiling, highlights coexistence of specific bacterial and archaeal representatives (especially, Prosthecochloris sp., Conexibacter sp., Crenarchaeota isolate (Caldivirga sp.), Metallosphaera sp., Pyrobaculum sp. and Acidianus sp.) in a digester with close proximity to geothermally active region (Site I) and their absence in a digester located far-off from geothermally active region (Site II). A Sörensen’s index of similarity of 83.33% and 66.66% for bacterial and archaeal community was observed in both the reactors, respectively.

Autochthonous microbial community associated with pine needle forest litterfall influences its degradation under natural environmental conditions

The slow natural degradation of chir pine (Pinus roxburghii) needle litterfall and its accumulation on forest floors have been attributed to its lignocellulosic complexities of the biomass. The present study offers a microbiological insight into the role of autochthonous microflora associated with pine needle litterfall in its natural degradation. The denaturing gradient gel electrophoresis (DGGE) fingerprinting indicated actinomycetes (Saccharomonospora sp., Glycomyces sp., Agrococcus sp., Leifsonia sp., Blastocatella sp., and Microbacterium sp.) as a dominant microbial community associated with pine needle litterfall with the absence of fungal decomposers. On exclusion of associated autochthonous microflora from pine litterfall resulted in colonization by decomposer fungi identified as Penicillium chrysogenum and Aspergillus sp., which otherwise failed to colonize the litterfall under natural conditions. The results, therefore, indicated that the autochthonous microbial community of pine needle litterfall (dominated by actinomycetes) obstructs the colonization of litter-degrading fungi and subsequently hinders the overall process of natural degradation of litterfall.

Tricalcium phosphate solubilization and nitrogen fixation by newly isolated Aneurinibacillus aneurinilyticus CKMV1 from rhizosphere of Valeriana jatamansi and its growth promotional effect

Aneurinibacillus aneurinilyticus strain CKMV1 was isolated from rhizosphere of Valeriana jatamansi and possessed multiple plant growth promoting traits like production of phosphate solubilization (260 mg/L), nitrogen fixation (202.91 nmol ethylene mL−1 h−1), indole-3-acetic acid (IAA) (8.1 μg/mL), siderophores (61.60%), HCN (hydrogen cyanide) production and antifungal activity. We investigated the ability of isolate CKMV1 to solubilize insoluble P via mechanism of organic acid production. High-performance liquid chromatography (HPLC) study showed that isolate CKMV1 produced mainly gluconic (1.34%) and oxalic acids. However, genetic evidences for nitrogen fixation and phosphate solubilization by organic acid production have been reported first time for A. aneurinilyticus strain CKMV1. A unique combination of glucose dehydrogenase (gdh) gene and pyrroloquinoline quinone synthase (pqq) gene, a cofactor of gdh involved in phosphate solubilization has been elucidated. Nitrogenase (nif H) gene for nitrogen fixation was reported from A. aneurinilyticus. It was notable that isolate CKMV1 exhibited highest antifungal against Sclerotium rolfsii (93.58%) followed by Fusarium oxysporum (64.3%), Dematophora necatrix (52.71%), Rhizoctonia solani (91.58%), Alternaria sp. (71.08%) and Phytophthora sp. (71.37%). Remarkable increase was observed in seed germination (27.07%), shoot length (42.33%), root length (52.6%), shoot dry weight (62.01%) and root dry weight (45.7%) along with NPK (0.74, 0.36, 1.82%) content of tomato under net house condition. Isolate CKMV1 possessed traits related to plant growth promotion, therefore, could be a potential candidate for the development of biofertiliser or biocontrol agent and this is the first study to include the Aneurinibacillus as PGPR.

A Review on the Implications of Interaction Between Human Pathogenic Bacteria and the Host on Food Quality and Disease

Abstract In the light of recent research endeavors much emphasis has been on understanding how fresh produce can be an important source of food-borne diseases. In today’s scenario where there is an increasing emphasis on organic produce, the chances of transmission of human pathogenic bacteria into the food chain are increasing, because of the bulk application of organic fertilizers in fields such as manure, which can be a potential source of enteric pathogens. The ability of enteric pathogens to cause human illness via fresh produce as a food matrix has been extensively documented in the last decade; however, research gaps exist especially in understanding the mechanisms of interaction between plants and human pathogenic bacteria. Evolutionary conservation in the cellular hubs of human pathogens exists that allows them to use plants as vectors in ways similar to the one they use for transmission via animal hosts. Reviewing the recent research developments in protein-protein interactions between the pathogen and the plant host, evaluation of human health risk by the presence of cross-domain pathogens and influence of ecological factors on survival and growth of enteric pathogens on fresh produce can lead to a better understanding and unravel the molecular basis of the interactions between human pathogenic bacteria and plant hosts.

Development and diversity of lactic acid producing bacteria and bifidobacteria in healthy full term Indian infants from Himachal Pradesh

Background/Aims The initial microbial colonization is a crucial step for the healthy development of an infant. Previous studies from India reported the dominance of target microbial species among Indian infants without any analysis on the diversity of target groups. This is the first study from India with an objective to investigate the establishment and diversity of lactic acid producing bacteria (LAB) and bifidobacteria in vaginally delivered, full term, breastfed infants for the first 4 months after birth. Methods Present study used polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) based sequence analysis of LAB and bifidobacteria in healthy infants. The results were used to compare the development and early colonization by LAB and bifidobacteria using diversity indices during the initial months of development of gut microbiota in infants. Results During the first 4 months, the Shannon diversity index (H) of LAB increased from 1.16 to 1.318 and for bifidobacteria the H increased from 0.975 to 1.293 (P<0.05). Higher Sorenson’s pair wise similarity coefficient was observed for LAB and bifidobacteria during 2nd and the 3rd month. The species of the genera Enterococcus, Streptococcus, and Lactobacillus were dominant among the LAB group whereas Bifidobacterium breve was dominant species among Bifidobacterium group. Conclusions Our results indicate that in breast fed infants, the microbial diversity of LAB and bifidobacteria increased during the period of study.

Insights into direct interspecies electron transfer mechanisms for acceleration of anaerobic digestion of wastes

Anaerobic digestion of waste organic biomass is a well-known process for conversion of biomass to bioenergy. However, global acceptability of anaerobic digestion process for renewable energy has often been undermined because of its inconsistent or lower rate of biogas production. The overall success of the anaerobic digestion process considerably depends on the interactions between the microbial communities within the digester. The electron transfer through interspecies hydrogen transfer between acetogens and methanogens is a major bottleneck for successful anaerobic digestion process. Recent studies have reported the role of biotic (pili and cytochromes) as well as abiotic (conductive materials) components to accelerate direct interspecies electron transfer between microbial communities in the digester. These transfer mechanisms via biotic components of exoelectrogenic bacteria and methanogenic archaea is thermodynamically more favorable over indirect interspecies electron transfer. However, the use of conductive materials in promoting anaerobic digestion process has been an area of research in the last few years. The process of direct interspecies electron transfer promoting anaerobic digestion process has been investigated evidently in pure microbial cultures; however, there are scanty reports on existence of direct interspecies electron transfer in mixed microbial consortia. The present review highlights the fundamentals and applications of direct interspecies electron transfer-promoted anaerobic digestion process at laboratory scale studies used to improve kinetics of methanogenesis.

Influence of cationic polyacrilamide flocculant on high-solids’ anaerobic digestion of sewage sludge under thermophilic conditions

ABSTRACT Treatment of sewage sludge (SS) by biodegradable polyacrylamide-based flocculants (PAM) is considered to be an effective way to increase total solids’ (TS) content prior to anaerobic digestion (AD). However, data on how PAM addition influences the efficiency of AD process are quite contradictory; moreover, no data are available for thermophilic AD (TAD). This study showed that at an optimal inoculum-to-substrate ratio (ISR, 55/45), PAM addition resulted in some decrease in initial methane production during the TAD of SS due to the formation of large flocs (up to 2–3 mm in diameter), which deteriorated the mass transfer. However, at non-optimal ISR (40/60), which led to the destabilization of TAD, PAM addition (40 mg/g TS) could restore the methanogenesis despite the inhibiting accumulation of volatile fatty acids (14–15 g/l) and pH drop (5.5). The observed positive effect of PAM-forced flocculation proposes a new interesting alternative for recovery of ‘soured’ reactors.