scispace - formally typeset
Search or ask a question
Author

Hovik Panosyan

Bio: Hovik Panosyan is an academic researcher from Yerevan State University. The author has contributed to research in topics: Bacilli & Proteobacteria. The author has an hindex of 10, co-authored 31 publications receiving 267 citations. Previous affiliations of Hovik Panosyan include University of Bergen & University of Nevada, Reno.

Papers
More filters
Journal ArticleDOI
TL;DR: A possible upper temperature limit of 60-65 °C for Nitrospira is suggested and the wide geographic range of NitroSpira species in geothermal environments is demonstrated.

41 citations

Journal ArticleDOI
TL;DR: Analysis of composition and structure of microbial communities inhabiting microbial mats in the source pools of two geothermal springs near the towns of Arzakan and Jermuk in Armenia suggests important roles for methanogenic archaea and AOA in the carbon and nitrogen biogeochemical cycles in these environments.
Abstract: Culture-independent and enrichment techniques, with an emphasis on members of the Archaea, were used to determine the composition and structure of microbial communities inhabiting microbial mats in the source pools of two geothermal springs near the towns of Arzakan and Jermuk in Armenia. Amplification of small-subunit rRNA genes using “universal” primers followed by pyrosequencing (pyrotags) revealed highly diverse microbial communities in both springs, with >99 % of pyrosequences corresponding to members of the domain Bacteria. The spring in Arzakan was colonized by a photosynthetic mat dominated by Cyanobacteria, in addition to Proteobacteria, Bacteroidetes, Chloroflexi, Spirochaeta and a diversity of other Bacteria. The spring in Jermuk was colonized by phylotypes related to sulfur, iron, and hydrogen chemolithotrophs in the Betaproteobacteria and Epsilonproteobacteria, along with a diversity of other Bacteria. Analysis of near full-length small subunit rRNA genes amplified using Archaea-specific primers showed that both springs are inhabited by a diversity of methanogens, including Methanomicrobiales and Methanosarcinales and relatives of Methanomassiliicoccus luminyensis, close relatives of the ammonia-oxidizing archaeon (AOA) “Candidatus Nitrososphaera gargensis”, and the yet-uncultivated Miscellaneous Crenarchaeotal Group and Deep Hydrothermal Vent Crenarchaeota group 1. Methanogenic enrichments confirmed the predicted physiological diversity, revealing methylotrophic, acetoclastic, and hydrogenotrophic methanogenesis at 45 and 55 °C, but not 65 °C. This is one of only a few studies combining cultivation-independent and -dependent approaches to study archaea in moderate-temperature (37–73 °C) terrestrial geothermal environments and suggests important roles for methanogenic archaea and AOA in the carbon and nitrogen biogeochemical cycles in these environments.

38 citations

Journal ArticleDOI
01 Sep 2019
TL;DR: Extremophilic microorganisms are a largely unexplored group of organisms that have the abilities to thrive in extreme conditions as mentioned in this paper, and they are also the most diverse organisms, present in about every nook and corner of the blue planet.
Abstract: Microorganisms are the most ubiquitous living entities on Earth. They are also the most diverse organisms, present in about every nook and corner of the blue planet. As per estimates only about 1% of the total microorganisms present on Earth have been discovered so far and there still are unexplored habitats where these omnipresent organisms may be present. Extremophilic microorganisms are a largely unexplored group that have the abilities to thrive in extreme conditions. These microbes have made useful adaptations in their genetic and metabolic machinery to thrive in the hostile conditions. Some of these microbes represent the very ancient life forms which must have thrived on Earth billions of years ago when the conditions were very different. In fact studying these microbes helps to find out how the evolution of life occurred on Earth and what type of conditions prevailed when life came on the planet. Extremophiles are categorized according to conditions in which they grow. Thermophiles/hyperthermophiles can be found in habitats with high or very high temperatures such as hydrothermal vents, volcanic sites, hot springs; psychrophiles flourish in cold habitats such as polar regions, on the mountains at high altitudes, deep inside the oceans; barophiles which love high pressure conditions are mainly found deep inside the oceans or sea; acidophiles at pH less than 5.0 or even near to 0.0, including habitats such as acid mine drainage sites, acidic lakes; alkalophiles thrive at highly alkaline pH such as in sodic lakes; halophiles love very high salt concentrations such as in sea, saline alkaline lakes; xerophiles can prosper in conditions with very low water availability which include deserts; metallophiles can tolerate and grow in presence of high concentrations of metals/heavy metals and there also are some other extremophilic forms which can even survive and grow in presence of high concentration of nuclides, pollutants such as poly hydroxyl alkanoates (PAHs), pesticides etc., and can be termed as pollution loving microbes which have evolved mainly due to anthropogenic activities. Sometimes, multiple stresses are present in the niche simultaneously and extremophiles which are able to thrive in such habitats are defined as polyextremophiles (such as thermoacidophiles, haloalkaliphiles and so on). There are innumerous examples of these fascinating organisms which have been discovered now and these include primarily prokaryotes (bacteria and archaea) and some eukaryotes (algae, yeast and fungi). Hyperthermophilic archaea Pyrolobus fumarii and Geogemma barossii have been reported with ability to tolerate temperature up to 121 °C. Another hyperthermophilic archaeon Methanopyrus kandleri strain 116 from deep sea hydrothermal field has been reported to withstand highest recorded temperature of 122 °C for any life form on Earth. Amongst psychrophiles, Psychrobacter cryopegellain isolated from Polar Regions of Siberian permafrost, Russia can survive up to − 20 °C. Thermophilic methanogens, Methanocaldococcus jannaschii and Methanothermococcus thermolithotrophicus are examples of barophilic microbes which have been isolated from high pressure niches of deep sea beds. Likewise, halophiles have been isolated from Great Salt Lake and Dead Sea. Halarsenatibacter silvermanii from a salt lake in USA is reported amongst the most halophilic microbe discovered and can survive in salt concentration of approximately 35%. Thiobacillus, Sulfolobus and Thermoplasma are some common genera that are considered to be very acidophilic in nature. Recently, Picrophilusoshimae and Picrophilustorridus have been included as the most acidophilic archaea from hot spring in Noboribetsu, Japan, which can grow at pH as low as 0.06. Haloalkalophilic Halomonas campisalis reported from Soap Lake, USA can grow at pH up to 12. Metallophiles which are able to resist high concentrations of heavy metals such as cadmium, cobalt, copper, lead, mercury, nickel, zinc and so on, have been isolated from volcanic areas, geothermal and hydrothermal vents and from industrially polluted sites. Xerotolerant and radiation * Naveen Kumar Arora nkarora.bbau@gmail.com

36 citations

Journal ArticleDOI
21 Aug 2015
TL;DR: Three novel methanotrophs are described, recovered from three different habitats in contrasting geographic regions and ecosystems: waterlogged rice-field soil and methane seep pond sediment from Bangladesh; and warm spring sediments from Armenia, which extend the knowledge of meethanotrophic Gammaproteobacteria and their physiology and adaptation to different ecosystems.
Abstract: Terrestrial methane seeps and rice paddy fields are important ecosystems in the methane cycle. Methanotrophic bacteria in these ecosystems play a key role in reducing methane emission into the atmosphere. Here, we describe three novel methanotrophs, designated BRS-K6, GFS-K6 and AK-K6, which were recovered from three different habitats in contrasting geographic regions and ecosystems: waterlogged rice-field soil and methane seep pond sediments from Bangladesh; and warm spring sediments from Armenia. All isolates had a temperature range for growth of 8–35 °C (optimal 25–28 °C) and a pH range of 5.0–7.5 (optimal 6.4–7.0). 16S rRNA gene sequences showed that they were new gammaproteobacterial methanotrophs, which form a separate clade in the family Methylococcaceae. They fell into a cluster with thermotolerant and mesophilic growth tendency, comprising the genera Methylocaldum-Methylococcus-Methyloparacoccus-Methylogaea. So far, growth below 15 °C of methanotrophs from this cluster has not been reported. The strains possessed type I intracytoplasmic membranes. The genes pmoA, mxaF, cbbL, nifH were detected, but no mmoX gene was found. Each strain probably represents a novel species either belonging to the same novel genus or each may even represent separate genera. These isolates extend our knowledge of methanotrophic Gammaproteobacteria and their physiology and adaptation to different ecosystems.

36 citations

Journal ArticleDOI
TL;DR: chemical composition and structure of the biopolymers, determined by GC–MS, HPAE-PAD and NMR, showed that both the two EPSs are heteropolymers composed by mannose as major monomer unit.
Abstract: The thermal ecosystems, including geothermal springs, are proving to be source of thermophiles able to produce extracellular polysaccharides (EPSs). Among the sixteen thermophilic bacilli isolated from sediment sampled from Arzakan geothermal spring, Armenia, two best EPSs producer strains were identified based on 16S rRNA gene sequence analysis and phenotypic characteristics, and designated as Geobacillus thermodenitrificans ArzA-6 and Geobacillus toebii ArzA-8 strains. EPSs production was investigated under different time, temperature and culture media’s composition. The highest specific EPSs production yield (0.27 g g−1 dry cells and 0.22 g g−1 dry cells for strains G. thermodenitrificans ArzA-6 and G. toebii ArzA-8, respectively) was observed after 24 h when fructose was used as sole carbon source at 65 °C and pH 7.0. Purified EPSs displayed a high molecular mass: 5 × 105 Da for G. thermodenitrificans ArzA-6 and 6 × 105 Da for G. toebii ArzA-8. Chemical composition and structure of the biopolymers, determined by GC–MS, HPAE-PAD and NMR, showed that both the two EPSs are heteropolymers composed by mannose as major monomer unit. Optical rotation values [α] D 25 °C of the two EPSs (2 mg ml−1 H2O) were − 142,135 and − 128,645 for G. thermodenitrificans ArzA-6 and G. toebii ArzA-8, respectively.

28 citations


Cited by
More filters
Journal ArticleDOI
TL;DR: Most surprisingly, close relatives to NOB perform complete nitrification (ammonia oxidation to nitrate) and this finding will have far-reaching implications for nitrification research.

542 citations

Journal ArticleDOI
TL;DR: A novel species in a new genus of the family Rikenellaceae is proposed, Acetobacteroides hydrogenigenes gen. nov, based on data from a strictly anaerobic, mesophilic, carbohydrate-fermenting, hydrogen-producing bacterium isolated from a reed swamp in China.
Abstract: A strictly anaerobic, mesophilic, carbohydrate-fermenting, hydrogen-producing bacterium, designated strain RL-C-T, was isolated from a reed swamp in China. Cells were Gram-stain-negative, catalase-negative, non-spore-forming, non-motile rods measuring 0.7-1.0 mu m in width and 3.0-8.0 mu m in length. The optimum temperature for growth of strain RL-C-T was 37 degrees C (range 25-40 degrees C) and pH 7.0-7.5 (range pH 5.7-8.0). The strain could grow fermentatively on yeast extract, tryptone, arabinose, glucose, galactose, mannose, maltose, lactose, glycogen, pectin and starch. The main end products of glucose fermentation were acetate, H-2 and CO2. Organic acids, alcohols and amino acids were not utilized for growth. Yeast extract was not required for growth; however, it stimulated growth slightly. Nitrate, sulfate, sulfite, thiosulfate, elemental sulfur and Fe(III) nitrilotriacetate were not reduced as terminal electron acceptors. Aesculin was hydrolysed but not gelatin. Indole and H2S were produced from yeast extract. The G+C content of the genomic DNA was 51.2 mol%. The major cellular fatty acids were iso-C-15:0, anteiso-C-(15:0) and C-16:0. The most abundant polar lipid of strain RL-C-T was phosphatidylethanolamine. 16S rRNA gene sequence analysis revealed that the isolate belongs to the uncultured Blvii28 wastewater-sludge group (http://www.arb-silva.de/) in the family Rikenellaceae of the phylum Bacteroidetes, and shared low sequence similarities with the related species Alistipes shahii WAL 8301(T) (81.8 %), Rikenella microfusus ATCC 29728(T) (81.7%) and Anaerocella delicata WN081(T) (80.9 %). On the basis of these data, a novel species in a new genus of the family Rikenellaceae is proposed, Acetobacteroides hydrogenigenes gen. nov., sp. nov. The type strain of the type species is RL-C-T (=JCM 17603(T)=DSM 24657(T)=CGMCC 1.5173(T)).

160 citations

Journal ArticleDOI
TL;DR: Analysis of 16S rRNA gene transcript amplicon sequencing in a temperate grassland soil subjected to century-long exposure to normal or extremely high copper levels showed that bioavailable copper had pronounced impacts on the structure of the transcriptionally active bacterial community, overruling other environmental factors.

117 citations

Journal ArticleDOI
TL;DR: Current knowledge about symbiotic interactions in the microbial world and their evolutionary impact, the status of eukaryogenetic models and the current challenges and perspectives ahead to reconstruct the evolutionary path to Eukaryotes are reviewed.

112 citations

Journal ArticleDOI
TL;DR: This review summarizes the current knowledge about morphological, physiological and genetic characteristics of the canonical and comammox Nitrospira and potential implications of comamm ox for the functional aspects of nitrogen removal have been highlighted.

95 citations