Genetic diversity in the moss Pohlia nutans on geothermal ground of Mount Rittmann, Victoria Land, Antarctica

The only known population of the moss Pohlia nutans in continental Antarctica occurs on geothermally heated ground of volcanic Mt. Rittmann in northern Victoria Land. Colonisation by this bryophyte is due to peculiar environmental characteristics of the geothermal ground, because mosses do not normally grow in Antarctica at such elevations. Specimens from several moss patches within two sites of 80 m² total area were analysed genetically to determine whether they all originated from a single colonisation event, whether the population is genetically diverse, and whether the temperature range of geothermal ground (17-35°C under moss colonies) affects rates of mutation. Both the RAPD technique and DNA sequencing of the conserved nuclear ribosomal RNA 18S-26S ITS region were used to compare this extremely isolated population with specimens of P. nutans from elsewhere in Antarctica. Like the moss Campylopus pyriformis on volcanic Mt. Melbourne, the Pohlia population exhibits low levels of genetic diversity and appears to be derived from a single immigration event followed by vegetative growth, mutation and dispersal.     

Anoxybacillus amylolyticus sp. nov., a thermophilic amylase producing bacterium isolated from Mount Rittmann (Antarctica)

A new thermophilic spore-forming strain MR3CT was isolated from geothermal soil located on Mount Rittmann in Antarctica. Strain MR3CT was Gram-positive, rod-shaped, occurring in pairs or filamentous. Growth was observed between 45 and 65 degrees C (optimum 61 degrees C) and at pH 5.0-6.5 (optimum pH 5.6). It was capable of utilizing galactose, trehalose, maltose and sucrose. The microorganism produced an exopolysaccharide and synthesized an extracellular constitutive amylolytic activity. The G + C content of DNA was 43.5 mol%. On the basis of 16S rRNA gene sequence similarity, strain MR3CT was shown to be related most closely to Anoxybacillus species. Chemotaxonomic data (major isoprenoid quinone-menaquinone-7; major fatty acid-iso-C15:0 and iso-C17:0) supported the affiliation of strain MR3C1T to the genus Anoxybacillus. The results of DNA-DNA hybridization, physiological and biochemical tests allowed genotypic and phenotypic differentiation of strain MR3CT from the validly published Anoxybacillus species. MR3CT therefore represents a new species, for which the name Anoxybacillus amylolyticus sp. nov., is proposed, with the type strain MR3CT (= ATCC BAA-872T = DSM 15939T = CIP 108338T).     

Interactions of arboreal yeast endophytes: an unexplored discipline

The value of healthy forest ecosystems is well known and trees in these systems form symbioses with a variety of living organisms. This review focuses on literature pertaining to the potential interactions of arboreal yeast endophytes with trees and their associated insects. Although very little is known about the symbioses of arboreal yeast endophytes, indications are that some of these unicellular fungi produce plant-growth promoting phytohormones, while others are antagonistic towards phytopathogens or are capable of producing pheromones that affect the behavior of insect herbivores. However, more research needs to be conducted to fully understand the role of arboreal yeast endophytes in ecosystem processes.     

Enumeration of Thermophilic Heterotrophs in Geothermally Heated Soils from Mount Erebus, Ross Island, Antarctica

Soil samples with temperatures up to 64°C were collected from Mount Erebus, an active volcano located on Ross Island, Antarctica. Acridine orange direct counts and most probable number counts of soil samples stored at 4°C for 2 months showed a wide variation in the number of thermophilic microorganisms in different soils. Organisms similar to Clostridium thermohydrosulfuricum, Bacillus schlegelii, and Bacillus acidocaldarius, as well as neutrophilic Bacillus strains, were isolated.     

Aromatic hydrocarbon-degrading bacteria from soil near Scott Base, Antarctica

Hydrocarbons persist in Antarctic soils when fuel oils such as JP8 jet fuel are spilled. For clean-up of hydrocarbon-contaminated soils in Antarctica, bioremediation has been proposed using hydrocarbon-degrading microbes indigenous to Antarctic soils. A number of alkane-degrading bacteria have been isolated previously from Antarctic soils. In this paper we describe the direct isolation of aromatic hydrocarbon-degrading bacteria from oil-contaminated Antarctic soil. Isolates that grew on JP8 jet fuel were characterised for their ability to degrade aromatic and aliphatic hydrocarbons and for growth at a range of temperatures. All isolates were gram-negative, oxidase-positive, rod-shaped bacteria. Representative strains were identified using 16S rDNA sequence analysis as either Sphingomonas spp. or Pseudomonas spp. Aromatic-degrading bacteria from Antarctic soils were psychrotolerant and appear similar to those found worldwide. Accepted: 27 September 1999     

Isolation and characterization of halotolerant Streptomyces radiopugnans from Antarctica soil

An actinomycete wild strain PM0626271 (= MTCC 5447), producing novel antibacterial compounds, was isolated from soil collected from Antarctica. The taxonomic status of the isolate was established by polyphasic approach. Scanning electron microscopy observations and the presence of LL‐Diaminopimelic acid in the cell wall hydrolysate confirmed the genus Streptomyces. Analysis of 16S rRNA gene sequence showed highest sequence similarity to Streptomyces radiopugnans (99%). The phylogenetic tree constructed using near complete 16S rRNA gene sequences of the isolate and closely related strains revealed that although the isolate fell within the S. radiopugnans gene subclade, it was allocated a different branch in the phylogenetic tree, separating it from the majority of the radiopugnans strains. Similar to type strain, S. radiopugnans R97^T, the Antarctica isolate displayed thermo tolerance as well as resistance to ⁶⁰Co gamma radiation, up to the dose of 15 kGy. However, media and salt tolerance studies revealed that, unlike the type strain, this isolate needed higher salinity for its growth. This is the first report of S. radiopugnans isolated from the Antarctica region. The GenBank/EMBL/DDBJ accession number for the 16S rRNA gene sequence of Streptomyces radiopugnans MTCC 5447 is JQ723477 .

Significance and Impact of the Study

The study presents the first report of isolation of Streptomyces radiopugnans from Antarctica. To date, there is only one publication regarding S. radiopugnans R97^T isolated from radiation‐polluted soil. Like the type strain, Antarctica isolate was thermotolerant and radiotolerant, but in addition, it required salts for growth and did not degrade phenol. We envisaged that metabolic pattern of the same species varies based on acclimatization in its native ecological habitat. Additionally, Antarctica isolate had produced novel antibacterial compounds (patent‐US2012/0156295). The study highlighted that least explored extreme regions like Antarctica are rich resources of novel microbial strains producing novel bioactive compounds.     

Clostridia in soil of the Antarctica.

From the soil in the area around the Syowa Station, the East Ongul Island, the Antarctica, a total of 193 strains of clostridia were isolated and identified. It was surprising that the soil samples taken from the places which were considered to be scarcely contaminated by human beings and animals contained many clostridia. One hundred and fifty-five strains were assigned to 11 species, including C. perfringens, C. bifermentans, C. sordellii, C. sporogenes, C. plagarum, C. paraperfringens, C. septicum, C. tertium, C. cadaveris, C. butyricum and C. felsineum, but 38 strains remained unidentified. C. perfringens, C. bifermentans and C. sordellii were isolated very frequently and C. sporogenes less frequently. All the strains of C. sordellii were nonpathogenic and had almost the same characteristics as those of C. bifermentans except for the attitude in the urease test. The peculiar distribution and characteristics of the clostridia in the Antarctic soil were discussed in comparison with those found in the soil in Japan.     

Potential for biodegradation of hydrocarbons in soil from the Ross Dependency, Antarctica

Oil spills occur in the Antarctic when fuel oils such as JP8 jet fuel are moved or stored. Hydrocarbons, both n-alkanes and aromatic compounds, have been detected in oil-contaminated soils of the Ross Dependency. In such areas hydrocarbon-degrading microbes, if naturally occurring, could be used for clean-up. Soil samples from oil-impacted and control sites were analysed for hydrocarbon-degrading microbes and for a range of parameters known to limit biodegradative activity. Soils were analysed for water content, pH, concentrations of nutrients (N and P) and electrical conductivity. Numbers of culturable heterotrophic bacteria and hydrocarbon degraders were greater in some of the oil-contaminated samples. Mineralisation studies with ¹⁴C-radiolabelled hexadecane and naphthalene demonstrated that nitrogen amendments significantly enhanced hydrocarbon mineralisation rates in an oil-impacted soil. Received: 30 June 1997 / Received revision: 15 September 1997 / Accepted: 19 September 1997     

Organic carbon cycling in Taylor Valley, Antarctica: quantifying soil reservoirs and soil respiration

Organic carbon reservoirs and respiration rates in soils have been calculated for most major biomes on Earth revealing patterns related to temperature, precipitation, and location. Yet data from one of the Earth's coldest, driest, and most southerly soil ecosystems, that of the McMurdo Dry Valleys of Antarctica, are currently not a part of this global database. In this paper, we present the first regional calculations of the soil organic carbon reservoirs in a dry valley ecosystem (Taylor Valley) and report measurements of CO₂ efflux from Antarctic soils. Our analyses indicate that, despite the absence of visible accumulations of organic matter in most of Taylor Valley's arid soils, this soil environment contained a significant percentage (up to 72%) of the seasonally unfrozen organic carbon reservoir in the terrestrial ecosystem. Field measurements of soil CO₂‐efflux in Taylor Valley soils were used to evaluate biotic respiration and averaged 0.10 ± 0.08 μmol CO₂ m^?2 s^?1. Laboratory soil microcosms suggested that this respiration rate was sensitive to increases in temperature, moisture, and carbon addition. Finally, a steady‐state calculation of the mean residence time for organic carbon in Taylor Valley soils was 23 years. Because this value contradicts all that is currently known about carbon cycling rates in the dry valleys, we suggest that the dry valley soil carbon dynamics is not steady state. Instead, we suggest that the dynamic is complex, with at least two (short‐ and long‐term) organic carbon reservoirs. We also suggest that organic carbon in the dry valley soil environment may be more important, and play a more active role in long‐term ecosystem processes, than previously believed.     

Bacterial diversity of a soil sample from Schirmacher Oasis, Antarctica.

The bacterial diversity of a soil sample collected in the vicinity of Lake Zub, Schirmacher Oasis, Antarctica, was determined both by establishing pure colonies of culturable bacteria and by cloning the total 16S rDNA of the soil and establishing the phylogeny of the clones. Analysis of the 16S rRNA gene clones indicated that the bacteria belonged to the classes alpha-proteobacteria, beta-proteobacteria, gamma-proteobacteria, Gemmatimonas, Bacteriodetes, Actinobacteria, Chloroflexi and Chlamydiae. In addition, seven clones were categorized as unidentified and unculturable in the classes of beta-Proteobacteria, Actinobacteria, Chloroflexi and Chlamydiae. Further, the culturable bacteria from the same site were identified as belonging to the genera Pseudomonas, Sphingobacterium, Arthrobacter, Micrococcus, Brevondimonas, Rhodococcus and Microbacterium. These results identify for the first time the presence of bacteria belonging to the genera Brevundimonas, Microbacterium, Rhodococcus, Serratia, Enterobacter, Rhodopseudomonas, Sphingomonas, Acidovorax, Burkholderia, Nevskia, Gemmatimonas, Xanthomonas and Flexibacter in Antarctica. Further, comparison of the Antarctic soil bacterial diversity with other cold habitats of Antarctica like from sediments, ice and cyanobacterial mat samples indicated that the bacterial diversity in soil was similar to the diversity observed in the continental shelf sediment sample. The Antarctic soil clones also resembled the bacterial diversity of soils from other geographical regions, but were unique in that none of the clones from the soil belonged to the uncultured Y, O, G, A and B groups common to all soil samples.     

Roseomonas alkaliterrae sp. nov., isolated from an alkali geothermal soil sample in Tengchong,Yunnan, south-west China

An alkalitolerant, thermotolerant and Gram-stain negative bacterium, designated strain YIM 78007^T, was isolated from an alkaline geothermal soil sample from Hehua hot spring, Tengchong, Yunnan province, south-west China. Cells of strain YIM 78007^T were observed to be aerobic and short rod-shaped. The colonies were observed to be orange-red, convex and circular. 16S rRNA gene sequence-based phylogenetic analysis showed that strain YIM 78007^T clustered with members of the genus Roseomonas (with similarities from 97.2 to 92.2 %). Optimal growth of strain YIM 78007 occurs at 40–50 °C and pH 8.0–10.0. The predominant ubiquinone was identified as Q-10 and the major fatty acids were identified as C_18:1 ω7c and C_16:0. The polar lipids were identified as diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, two unidentified aminolipids and one unknown phospholipid. The G + C content of the genomic DNA was determined to be 63 mol %. The levels of DNA–DNA hybridization relatedness between strain YIM 78007^T and its closet neighbours (Roseomonas lacus JCM 13283^T and Roseomonas terrae JCM 14592^T) were well below the threshold required for the proposal of a novel species. The results of physiological and biochemical characteristics, the phylogenetic analysis, as well as low DNA–DNA hybridization values, allowed the phenotypic and genotypic differentiation of strain YIM 78007^T from its closest phylogenetic neighbours. Therefore, strain YIM 78007^T is considered to represent a novel species of the genus Roseomonas, for which the name Roseomonas alkaliterrae sp. nov. is proposed. The type strain is YIM 78007^T (=BCRC 80644^T = JCM 19656^T).     

Characterization of bacterial strains capable of desulphurisation in soil and sediment samples from Antarctica

The presence of sulphur in fossil fuels and the natural environment justifies the study of sulphur-utilising bacterial species and genes involved in the biodesulphurisation process. Technology has been developed based on the natural ability of microorganisms to remove sulphur from polycyclic aromatic hydrocarbon chains. This biotechnology aims to minimise the emission of sulphur oxides into the atmosphere during combustion and prevent the formation of acid rain. In this study, the isolation and characterization of desulphurising microorganisms in rhizosphere and bulk soil samples from Antarctica that were either contaminated with oil or uncontaminated was described. The growth of selected isolates and their capacity to utilise sulphur based on the formation of the terminal product of desulphurisation via the 4S pathway, 2-hydroxybiphenyl, was analysed. DNA was extracted from the isolates and BOX-PCR and DNA sequencing were performed to obtain a genomic diversity profile of cultivable desulphurising bacterial species. Fifty isolates were obtained showing the ability of utilising dibenzothiophene as a substrate and sulphur source for maintenance and growth when plated on selective media. However, only seven genetically diverse isolates tested positive for sulphur removal using the Gibbs assay. DNA sequencing revealed that these isolates were related to the genera Acinetobacter and Pseudomonas.     

Hexadecane mineralization activity in ornithogenic soil from Seabee Hook,Cape Hallett,Antarctica

Ornithogenic soils that form in penguin rookeries contain high levels of organic carbon and nitrogen. On Seabee Hook, Cape Hallett, Antartica, ornithogenic soil was contaminated with hydrocarbons following establishment of a scientific research station. In these soils hydrocarbon biodegradation could be supported by available soil nitrogen. Hexadecane mineralization activity was detected in vitro in ornithogenic soil when incubated at 5 or 15°C. At 5°C the extent of hexadecane mineralization was higher in hydrocarbon-contaminated soil than in uncontaminated soil. Alkane-degrading bacteria isolated from Seabee Hook soil were identified as Rhodococcus or Gordonia spp. or an unclassified Corynebacterineae. The alkane degraders grew on n-alkanes from heptane (C8) to eicosane (C20) and pristane, and utilized uric acid or ammonium nitrate as nitrogen source. All of the isolates possessed urease activity. Results of this study indicate biodegradation of hydrocarbons may contribute to the natural attenuation of oil spills in ornithogenic surface soils in summer.     

Actinomycetes: an unexplored microorganisms for plant growth promotion and biocontrol in vegetable crops

Actinomycetes, a Gram positive bacteria, well reported as a source of antibiotics, also possess potential to control various plant pathogens, besides acting as plant growth promoting agent. Chemicals in different forms are extensively being used in vegetable farming, adversely affecting the environment and consumer health. Microbial agent like actinomycetes can substantially replace these harmful chemicals, and have now started finding a place as an important input in to farming practices. Only selected vegetable crops belonging to 11 different families have been explored with use of actinomycetes as biocontrol and plant growth promoting agent till now. It provides ample opportunities to vegetable researchers, to further explore with use of this very important group of microorganisms, in order to achieve even higher production level of safe vegetables. Mycostop and Actinovate are two actinomycetes based formulations globally available for use in vegetable farming as a substitute for chemical formulations. Present review article has summarized the literature available on use of actinomycetes in vegetable farming. Existing wide gap in knowledge, and potential thrust areas for future research have also been projected.     

Rates of spontaneous mutation in an archaeon from geothermal environments.

To estimate the efficacy of mechanisms which may prevent or repair thermal damage to DNA in thermophilic archaea, a quantitative assay of forward mutation at extremely high temperature was developed for Sulfolobus acidocaldarius, based on the selection of pyrimidine-requiring mutants resistant to 5-fluoro-orotic acid. Maximum-likelihood analysis of spontaneous mutant distributions in wild-type cultures yielded maximal estimates of (2.8 +/- 0.7) x 10(-7) and (1.5 +/- 0.6) x 10(-7) mutational events per cell per division cycle for the pyrE and pyrF loci, respectively. To our knowledge, these results provide the first accurate measurement of the genetic fidelity maintained by archaea that populate geothermal environments. The measured rates of forward mutation at the pyrE and pyrF loci in S. acidocaldarius are close to corresponding rates reported for protein-encoding genes of Escherichia coli. The normal rate of spontaneous mutation in E. coli at 37 degrees C is known to require the functioning of several enzyme systems that repair spontaneous damage in DNA. Our results provide indirect evidence that S. acidocaldarius has cellular mechanisms, as yet unidentified, which effectively compensate for the higher chemical instability of DNA at the temperatures and pHs that prevail within growing Sulfolobus cells.     

Extracellular hydrolase enzyme production by soil fungi from King George Island, Antarctica

Various microbial groups are well known to produce a range of extracellular enzymes and other secondary metabolites. However, the occurrence and importance of investment in such activities have received relatively limited attention in studies of Antarctic soil microbiota. In order to examine extracellular enzyme production in this chronically low-temperature environment, fungi were isolated from ornithogenic, pristine and human-impacted soils collected from the Fildes Peninsula, King George Island, Antarctica during the austral summer in February 2007. Twenty-eight isolates of psychrophilic and psychrotolerant fungi were obtained and screened at a culture temperature of 4°C for activity of extracellular hydrolase enzymes (amylase, cellulase, protease), using R2A agar plates supplemented with (a) starch for amylase activity, (b) carboxymethyl cellulose and trypan blue for cellulase activity or (c) skim milk for protease activity. Sixteen isolates showed activity for amylase, 23 for cellulase and 21 for protease. One isolate showed significant activity across all three enzyme types, and a further 10 isolates showed significant activity for at least two of the enzymes. No clear associations were apparent between the fungal taxa isolated and the type of source soil, or in the balance of production of different extracellular enzymes between the different soil habitats sampled. Investment in extracellular enzyme production is clearly an important element of the survival strategy of these fungi in maritime Antarctic soils.     

Relative availability of inorganic N-pools shifts under land use change: An unexplored variable in soil carbon dynamics

Land use change (LUC) may detrimentally affect the soil organic carbon (SOC) within different soil fractions; directly supplemented by significant contribution to soil CO₂ efflux (SCE). To understand the governing mechanism, experimental data were collected for SOC and SCE along with soil physico-chemical, microbial and aggregate characteristics across adjacent secondary forest (SF)-grassland (GL)-cropland (CL) sequence in dry tropical ecosystems. A significant change in SOC and SCE was observed from SF to GL and CL systems, respectively; though moderately from GL to CL system. Respective decrease in SOC (31 and 42%); soil ammonium-N to nitrate-N ratio (ANR; 96 and 86%), microbial biomass C (MBC; 30 and 50%), nitrogen (MBN; 6 and 33%) and MBC/MBN ratio (25 and 24%); whereas increase in SCE (43 and 57%) and soil nitrate-N availability (340 and 592%) was observed from SF to GL and CL systems. Moreover, aggregate physical distribution shifted toward smaller size fractions; whereas aggregate-associated total C and KMnO₄-labile-C concentration and carbon management index (CMI) across aggregate-size fractions decreased linearly with the land use sequence. SOC was majorly governed by macro-aggregate water stability (WAS_macro) and MBC; whereas SCE by CMI of macro-aggregate (CMI_macro) fraction. Furthermore, the ANR showed positive correlation with microbial (i.e. MBC and MBC/MBN ratio) and macro-aggregate physical (i.e. WAS_macro) and chemical stability (i.e. CMI_macro). It indicates that a shift in the microbial community with the land use may affect the relative availability of inorganic N pools and associated aggregate characteristics. Thus, our results indicate that a shift in ANR with LUC may be an unexplored and crucial indicator of soil C dynamics mediating quantitative and qualitative changes in microbial and aggregate characteristics in dry tropical ecosystems. Further, a critical emphasis is needed on the relationship of SOC dynamics with ANR for future studies at various spatiotemporal scales worldwide to recognize its potential role as ecological indicator of SOC dynamics. Also, its inclusion under climatic models may help to better predict the future climate.     

Richness and bioactivity of culturable soil fungi from the Fildes Peninsula,Antarctica

Since the discovery of penicillin, fungi have been an important source of bioactive natural products. However, as a specific resource, the bioactive potentiality and specificity of fungal metabolites from the Antarctic region have had little attention. In this paper, we investigated the diversity patterns and biological activities of cultivable fungi isolated from soil samples in Fildes Peninsula, King George Island, Antarctica. Fungal communities showed low abundance and diversity; a total of 150 cultivable fungi were isolated from eight soil samples. After being dereplicated by morphological characteristics and chemical fingerprints, 47 fungal isolates were identified by ITS-rDNA sequencing. We confirmed that these isolates belonged to at least 11 different genera and clustered into nine groups corresponding to taxonomic orders in the phylogenetic analysis. Using two different fermentation conditions, 94 crude extracts acquired from the abovementioned different metabolite characteristic isolates were screened by bioactivity assay and 18 isolates produced biologically active compounds. Compared with HPLC–DAD–UV fingerprint analysis of culture extracts and standard compounds, two bioactive components secalonic acid and chetracins were identified. Our research suggests that the abundance and diversity of Antarctic cultivable fungal communities exhibit unique ecological characteristics and potential producers of novel natural bioactive products.     

Potential for bioremediation of fuel‐contaminated soil in Antarctica

A preliminary investigation was conducted to identify the presence of bacteria in fuel‐contaminated Antarctic soil that could potentially be used to bioremediate the contaminated soil at McMurdo Station and other sites in Antarctica. The ability of soil microorganisms to metabolize fuels under the extreme climatic and oligotrophic conditions of Antarctica was of concern. Bacteria were isolated from fuel‐contaminated soil on site at McMurdo Station. Bacteria from noncontaminated soil near the station were also studied for comparison. The Antarctic soil microorganisms exhibited the ability to endure cold and oligotrophic environments. Experiments also showed that bacteria from the fuel spill site were active in their contaminated environment and that acclimation to xenobiotic compounds was necessary. Application of bioremediation in the extreme environmental conditions found at McMurdo Station, Antarctica, were also considered. The possibility of altering environmental factors necessary to adequately support in situ bioremediation in this extreme climate is discussed.