Environmental influences on bacterial diversity of soils on Signy Island,maritime Antarctic

Soil bacterial diversity at environmentally distinct locations on Signy Island, South Orkney Islands was examined using the denaturing gradient gel profiling approach. A range of chemical variables in soils at each site was determined in order to describe variation between locations. No apparent differences in Shannon Diversity Index (H′) were observed. However, as revealed in an analysis of similarity (ANOSIM), the dominant bacterial communities of all eight studied locations were significantly different. Within this, higher levels of similarity were observed between penguin rookeries, seal wallows and vegetated soils, all of which share varying levels of impact from vertebrate activity, in contrast with more barren soil. In addition, the lowest H′ value was detected from the latter soil which also has the most extreme environmental conditions, and its bacterial community has the greatest genetic distance from the other locations. DGGE analyses indicated that the majority of the excised and sequenced bands were attributable to the Bacteroidetes. Across a range of ten environmental variables, multivariate correlation analysis suggested that a combination of pH, conductivity, copper and lead content potentially contributed explanatory value to the measured soil bacterial diversity.     

Diversity of endophytic fungi associated with bryophyte in the maritime Antarctic (King George Island)

Bryophytes comprise one of the richest microfungal microhabitats in the Antarctic environment. The maritime Antarctic is very vulnerable to rapid environmental change caused by global warming. The aim of this study was to investigate the importance of bryophytes as a microhabitat for fungal species in the maritime Antarctic by surveying endophytic fungal diversity from several bryophytes including Andreaea sp., Barbilophozia hatcheri, Chorisodontium aciphyllum, Polytrichum alpinum, Polytrichum strictum, Sanionia uncinata, and Warnstorfia sarmentosa. We collected 13 bryophyte samples at four localities on Barton Peninsula, King George Island. In total, 31 endophytic fungi morphotypes were isolated from bryophyte tissues by a thorough surface sterilization method. Using internal transcribed spacer sequence analysis, 16 endophytic fungal strains belonging to Ascomycota (12), Basidiomycota (1), Oomycota (1), and Zygomycota (2) phyla were obtained. Our results suggest the presence of a diverse range of fungal species even in a very limited area, and those bryophytes play an important role in conserving fungal diversity in this harsh environment. Growth rate measurements at a wide range of temperatures confirmed that most of the fungal strains were both mesophilic and psychrotolerant. This is the first report of endophytic fungi in Antarctic moss tissue by fluorescence in situ hybridization.     

Dispersal of moss propagules on Signy Island, maritime Antarctic

Aerobiological studies were conducted for >1 year using arrays of rotorod samplers at three sites on Signy Island, South Orkney Islands, maritime Antarctic. Spores of five bryophyte taxa were identified, all of which are known to be widely distributed and fruit frequently on the island. Spore size did not appear to influence potential for dispersal, with spores of all five taxa being captured 0.5–1 km from their nearest known source plants. Spores were more abundant than plant fragments, although the occurrence of both propagule types in the air was small in comparison to the ground cover of mosses, and the occurrence of lichen propagules in the air. Spores were captured over a much longer period of the year (including the winter months) than that in which sporophyte dehiscence is thought to occur on Signy Island; possible reasons for this are discussed. Received: 20 February 1997 / Accepted: 7 June 1997     

Identification of actinomycete communities in Antarctic soil from Barrientos Island using PCR-denaturing gradient gel electrophoresis

The diversity of specific bacteria taxa, such as the actinomycetes, has not been reported from the Antarctic island of Barrientos. The diversity of actinomycetes was estimated with two different strategies that use PCR-denaturing gradient gel electrophoresis. First, a PCR was applied, using a group-specific primer that allows selective amplification of actinomycete sequences. Second, a nested-PCR approach was used that allows the estimation of the relative abundance of actinomycetes within the bacterial community. Molecular identification, which was based on 16S rDNA sequence analysis, revealed eight genera of actinomycetes, Actinobacterium, Actinomyces, an uncultured Actinomycete, Streptomyces, Leifsonia, Frankineae, Rhodococcus, and Mycobacterium. The uncultured Actinomyces sp and Rhodococcus sp appear to be the prominent genera of actinomycetes in Barrientos Island soil. PCR-denaturing gradient gel electrophoresis patterns were used to look for correlations between actinomycete abundance and environmental characteristics, such as type of rookery and vegetation. There was a significant positive correlation between type of rookery and abundance of actinomycetes; soil samples collected from active chinstrap penguin rookeries had the highest actinomycete abundance. Vegetation type, such as moss, which could provide a microhabitat for bacteria, did not correlate significantly with actinomycete abundance.     

Vegetation of Barton Peninsula in the neighbourhood of King Sejong Station (King George Island,maritime Antarctic)

Plant communities were studied on Barton Peninsula around King Sejong Station on King George Island, maritime Antarctic. The objective of this study was to document the occurrence and distribution of plant assemblages to provide the bases for monitoring the effects of environmental changes and human impact on the vegetation of this area. Approximately 47% of the investigated area was covered by vegetation. Crustose lichens showed the highest mean cover (21%) among vegetation components. The total mean cover of the four dominant taxa, together with the other three major subdominant components, i.e., Usnea spp., Andreaea spp. and Sanionia georgico-uncinata, was 78.2% of the total cover of all the species. Lichen cover and species diversity increased with altitude and the time of exposure from snow. Lichens contributed substantially more to the increased species density and diversity than did bryophytes. Ten plant communities were recognized within the study area. All of them belong to the Antarctic cryptogam tundra formation; they were grouped into four subformations: fruticose lichen and moss cushion subformation, crustose lichen subformation, moss carpet subformation and moss hummock subformation. The moss turf subformation was not found on this region. The Antarctic herb tundra formation was also not found; however, the populations of both Antarctic vascular plants have rapidly expanded around Barton Peninsula in recent years, which may allow development of the Antarctic herb tundra formation in the future.     

First record of Trichoceridae (Diptera) in the maritime Antarctic

During the austral summer of 2006–07, abundant Diptera were found in the sewage system of the Base Científica Antártica Artigas on King George Island. These are here identified as Trichocera (Saltrichocera) maculipennis (Diptera: Trichoceridae), a Holarctic species widely distributed in the Northern Hemisphere which has been introduced to some sub-Antarctic islands, but never been recorded in the maritime Antarctic. The distribution of the fly on King George Island indicates that it has been introduced by human agency. Although its origin is unclear, adult specimens have distinctive morphological features rarely represented in autochthonous populations in Europe. To date, larvae have been found only in the Artigas Base sewage system, but adults have been observed around the buildings and more widely in the vicinity. Given the species’ natural northern range, habitats and feeding preferences, it is likely to have good preadaptation permitting survival in the natural terrestrial ecosystems of the maritime Antarctic. We recommend that urgent eradication efforts are made.     

Structure and diversity of soil algal communities from Cierva Point (Antarctic Peninsula)

Cyanobacteria and eukaryotic algae, together with bacteria and fungi, are known to be primary colonizers of mineral soils throughout Antarctica. Their species diversity and soil coverage were studied in 18 soil polygons located at Cierva Point, Antarctic Peninsula. Undisturbed assemblages were dominated by filamentous Cyanobacteria and diatoms, whilst almost 40% of the 49 species recorded were observed only after enrichment culture. Nearly all of the isolates from enrichment cultures were Chlorophyta and Tribophyceae. This revealed a higher degree of complexity than reported for similar communities on Signy Island. Water content and concentrations of nutrients were determined at four representative sites, and did not appear to account for the large inter-polygon variation found in species composition and relative frequencies of occurrence. Variables describing community development were not significantly correlated with either area of the polygons or the minimum distance between them. This suggested that these features are not an important short-range barrier to dispersal for those “weed” species dominating the community. Conversely, the relative frequencies of some of the most common species showed significant correlations with species diversity and soil coverage, and it is suggested that biotic interactions could account to a larger extent for community structure than previously reported from Signy Island fellfields. Accepted: 12 October 1999     

Carbon and nitrogen isotope composition of vegetation on King George Island,maritime Antarctic

We report abundance of ¹³C and ¹⁵N contents in terrestrial plants (mosses, lichens, liverworts, algae and grasses) from the area of Barton Peninsula (King George Island, maritime Antarctic). The investigated plants show a wide range of δ¹³C and δ¹⁵N values between −29.0 and −20.0‰ and between −15.3 and 22.8‰, respectively. The King George Island terrestrial plants show species specificity of both carbon and nitrogen isotope compositions, probably due to differences in plant physiology and biochemistry, related to their sources and in part to water availability. Carbon isotope compositions of Antarctic terrestrial plants are typical of the C₃ photosynthetic pathway. Lichens are characterized by the widest carbon isotope range, from −29.0 to −20.0‰. However, the average δ¹³C value of lichens is the highest (−23.6 ± 2.8‰) among King George Island plants, followed by grasses (−25.6 ± 1.7‰), mosses (−25.9 ± 1.6‰), liverworts (−26.3 ± 0.5‰) and algae (−26.3 ± 1.2‰), partly related to habitats controlled by water availability. The δ¹⁵N values of moss samples range widest (−9.0 to 22.8‰, with an average of 4.6 ± 6.6‰). Lichens are on the average most depleted in ¹⁵N (mean = −7.4 ± 6.4‰), whereas algae are most enriched in ¹⁵N (10.0 ± 3.3‰). The broad range of nitrogen isotope compositions suggest that the N source for these Antarctic terrestrial plants is spatially much variable, with the local presence of seabird colonies being particularly significant.     

Phylogenetic analysis of the succession of bacterial communities in the Great South Bay (Long Island)

Bacterial community composition and succession were examined over the course of the summer season in the Great South Bay, Long Island, NY, USA, using a 16S rDNA clone library approach. There was a progression of changes in dominant species in the libraries during the summer of 1997. The July library had several groups dominant, the SAR407 relatives of the alpha-Proteobacteria (24%) and the SAR86 (18%), sulfur-oxidizing symbiont relatives (8%) of the gamma-Proteobacteria, and unidentified Cytophaga-Flexibacter representatives (22%). In August, the Cytophaga-Flexibacter (Gelidibacter sp. and unidentified Cytophaga-Flexibacter representative) and Cyanobacteria (Synechococcus sp.) increased to 28% and 14%, respectively. High GC Gram-positives appeared at 18%, and beta-Proteobacteria (Ralstonia sp.) at 10%. By September these groups had either declined or were absent, while the SAR86 cluster, Pseudoalteromonas and Alteromonas of the gamma-Proteobacteria were dominant in the community (61%). The dominance of open ocean bacteria along with the presence of Aureococcus anophagefferens (Pelagophyceae) in July suggests possible open ocean coupling to bloom events. Many clones in this study were related to previously described clones from a wide distribution of marine environments, substantiating the cosmopolitan nature of pelagic bacteria. Only one isolated bacterium was closely related to 16S rDNA found in the August library.     

Soil properties and distributions of invertebrates and bacteria from King George Island (Arctowski Station), maritime Antarctic

Soils of the Admiralty Bay region at King George Island, maritime Antarctic are described and analysed for invertebrates and microorganisms. Results showed a great variety of soils: cambisols, umbrisols, regosols, podzols, leptosols, gleysols and relic ornithogenic soils were found. Surface layers, especially of cambisols, umbrisols and podzols, showed a diverse fauna, governed by nematodes, collemboles and mites. The bacterial flora is analysed for total counts and biomass distribution in different layers using epifluorescence microscopy. Influences of soil organic matter can be described by different patterns of mean bacterial cell volumes related to soil cover and depth distributions. Received: 21 February 1997 / Accepted: 28 April 1997     

Effect of 2,4,6-trinitrotoluene on soil bacterial communities

To gain insight into the impact of 2,4,6-trinitrotoluene (TNT) on soil microbial communities, we characterized the bacterial community of several TNT-contaminated soils from two sites with different histories of contamination and concentrations of TNT. The amount of extracted DNA, the total cell counts and the number of CFU were lower in the TNT-contaminated soils. Analysis of soil bacterial diversity by DGGE showed a predominance of Pseudomonadaceae and Xanthomonadaceae in the TNT-contaminated soils, as well as the presence of Caulobacteraceae. CFU from TNT-contaminated soils were identified as Pseudomonadaceae, and, to a lesser extent, Caulobacteraceae. Finally, a pristine soil was spiked with different concentrations of TNT and the soil microcosms were incubated for 4 months. The amount of extracted DNA decreased in the microcosms with a high TNT concentration [1.4 and 28.5 g TNT/kg (dry wt) of soil] over the incubation period. After 7 days of incubation of these soil microcosms, there was already a clear shift of their original flora towards a community dominated by Pseudomonadaceae, Xanthomonadaceae, Comamonadaceae and Caulobacteraceae. These results indicate that TNT affects soil bacterial diversity by selecting a narrow range of bacterial species that belong mostly to Pseudomonadaceae and Xanthomonadaceae.     

Phylogenetic analysis of the composition of bacterial communities in human-exploited coastal environments from Mallorca Island (Spain)

The phylogenetic analysis of bacterial communities in environments receiving anthropogenic impact could help us to understand its effects and might be useful in the development of monitoring or management strategies. A study of the composition of 16S rDNA clone libraries prepared from bacterial communities in water samples from a marina and a beach on the coast of Mallorca (W. Mediterranean) was undertaken at two time points, corresponding to periods of maximum and minimum anthropogenic use of this area for nautical and recreational activities. Libraries generated from the marina were significantly different from those from the beach and a non-impacted, bay sample. In the marina, a predominance of sequence types was observed related to bacterioplankton from nutrient-enriched environments or typically associated with phytoplankton, such as certain phylotypes of the Roseobacter clade, OM60 clade and Bacteroidetes. Similar results were found in the summer beach library but not in the winter one, in which there was an increase in the number of clones from oligotrophic groups, in agreement with lower chlorophyll content and bacterial counts. Therefore, nutrient enrichment seemed to be an important driver of the composition of bacterial communities in sites receiving direct human impact. Interesting sequence types from the Cryomorphaceae and group agg58 (Bacteroidetes) were exclusively found in beach libraries, and the reasons for this distribution deserve further study. Clones related to putative hydrocarbon-degrading bacteria of the genus Acinetobacter were observed in the marina, in agreement with a certain degree of pollution at this site. Non-marine sequences belonging to the Actinobacteria predominated over marine groups in the summer library from the marina and, therefore, unusual communities might be transiently present in this enclosed environment. Overall, the composition of the bacterial communities in these environments agreed well with the defining characteristics of the environments sampled.     

Distribution patterns in the biomass of macrozoobenthic communities in Admiralty Bay (King George Island, South Shetlands, Antarctic)

The distribution patterns of macrozoobenthic communities as shown by the biomass of the higher taxa were investigated in Admiralty Bay. Material was collected at depths ranging from 4 to 500 m (102 quantitative samples), representing the full depth range of this basin and including areas characterized by the different levels of glacial influence. Five community groups were distinguished by multivariate analysis (clustering, MDS) based on the Bray--Curtis similarity index. In the Ezcurra Inlet, the area characterized by intensive glacial processes resulting in a high sedimentation rate, the distribution of biomass was not depth related, but was associated with the intensity of glacial disturbance along the axis of the fjord. The innermost part of this fjord, which receives strong outflows from glaciers, had a low biomass value (2.9 g/0.1 m²) and was dominated by polychaetes. The middle part of the fjord which is not so heavily disturbed had higher biomass values (46.1 g/0.1 m²) due to the dominance of bivalves. A clear depth gradient of biomass distribution was observed in bottom areas located far from glaciers, in the central basin of the bay, with three zones within the depth ranges 4–30, 40–380, and 400–500 m. The highest mean biomass values (92.5 g/0.1 m²) were found in the middle sublittoral (40–380 m) dominated by ascidians. In the shallow and deep assemblages, the biomass was lower (33.8 g/0.1 and 30.9 g/0.1 m² respectively), most probably associated with the ice disturbance in the shallows and lower food supply in the deepest part of the shelf.     

Diversity and structure of bacterial communities in Arctic versus Antarctic pack ice

A comprehensive assessment of bacterial diversity and community composition in arctic and antarctic pack ice was conducted through cultivation and cultivation-independent molecular techniques. We sequenced 16S rRNA genes from 115 and 87 pure cultures of bacteria isolated from arctic and antarctic pack ice, respectively. Most of the 33 arctic phylotypes were >97% identical to previously described antarctic species or to our own antarctic isolates. At both poles, the alpha- and gamma-proteobacteria and the Cytophaga-Flavobacterium group were the dominant taxonomic bacterial groups identified by cultivation as well as by molecular methods. The analysis of 16S rRNA gene clone libraries from multiple arctic and antarctic pack ice samples revealed a high incidence of closely overlapping 16S rRNA gene clone and isolate sequences. Simultaneous analysis of environmental samples with fluorescence in situ hybridization (FISH) showed that approximately 95% of 4',6'-diamidino-2-phenylindole (DAPI)-stained cells hybridized with the general bacterial probe EUB338. More than 90% of those were further assignable. Approximately 50 and 36% were identified as gamma-proteobacteria in arctic and antarctic samples,respectively. Approximately 25% were identified as alpha-proteobacteria, and 25% were identified as belonging to the Cytophaga-Flavobacterium group. For the quantification of specific members of the sea ice community, new oligonucleotide probes were developed which target the genera Octadecabacter, Glaciecola, Psychrobacter, Marinobacter, Shewanella, and Polaribacter: High FISH detection rates of these groups as well as high viable counts corroborated the overlap of clone and isolate sequences. A terrestrial influence on the arctic pack ice community was suggested by the presence of limnic phylotypes.     

Temperature adaptation of soil bacterial communities along an Antarctic climate gradient: predicting responses to climate warming

Soil microorganisms, the central drivers of terrestrial Antarctic ecosystems, are being confronted with increasing temperatures as parts of the continent experience considerable warming. Here we determined short‐term temperature dependencies of Antarctic soil bacterial community growth rates, using the leucine incorporation technique, in order to predict future changes in temperature sensitivity of resident soil bacterial communities. Soil samples were collected along a climate gradient consisting of locations on the Antarctic Peninsula (Anchorage Island, 67 °34′S, 68 °08′W), Signy Island (60 °43′S, 45 °38′W) and the Falkland Islands (51 °76′S 59 °03′W). At each location, experimental plots were subjected to warming by open top chambers (OTCs) and paired with control plots on vegetated and fell‐field habitats. The bacterial communities were adapted to the mean annual temperature of their environment, as shown by a significant correlation between the mean annual soil temperature and the minimum temperature for bacterial growth (T_min). Every 1 °C rise in soil temperature was estimated to increase T_min by 0.24–0.38 °C. The optimum temperature for bacterial growth varied less and did not have as clear a relationship with soil temperature. Temperature sensitivity, indicated by Q₁₀ values, increased with mean annual soil temperature, suggesting that bacterial communities from colder regions were less temperature sensitive than those from the warmer regions. The OTC warming (generally <1 °C temperature increases) over 3 years had no effects on temperature relationship of the soil bacterial community. We estimate that the predicted temperature increase of 2.6 °C for the Antarctic Peninsula would increase T_min by 0.6–1 °C and Q₁₀ (0–10 °C) by 0.5 units.     

Short-term effects of amoxicillin on bacterial communities in manured soil

Antibiotic-resistant bacteria, nutrients and antibiotics that enter the soil by means of manure may enhance the proportion of bacteria displaying antibiotic resistance among soil bacteria and may affect bacterial community structure and function. To investigate the effect of manure and amoxicillin added to manure on soil bacterial communities, microcosm experiments were performed with two soil types and the following treatments: (1) nontreated, (2) manure-treated, (3) treated with manure supplemented with 10 mg amoxicillin kg(-1) soil and (4) treated with manure supplemented with 100 mg amoxicillin kg(-1) soil, with four replicates per treatment. Manure significantly increased the total CFU count and the amoxicillin-resistant CFU count of both soil types. However, only the soil with a history of manure treatment showed a significant increase in the relative number of amoxicillin-resistant bacteria as a result of amoxicillin amendment. The majority of plasmids exogenously isolated from soil originated from soil treated with amoxicillin-supplemented manure. All 16 characterized plasmids carried the bla-TEM gene, and 10 of them belonged to the IncN group. The bla-TEM gene was detected in DNA directly extracted from soil by dot-blot hybridization of PCR amplicons and showed an increased abundance in soil samples treated with manure. Molecular fingerprint analysis of 16S rRNA gene fragments amplified from soil DNA revealed significant effects of manure and amoxicillin on the bacterial community of both soils.     

Notes on the lichen genus Lepraria from maritime (South Shetlands) and continental (Schirmacher and Bunger Oases) Antarctica

Material of the genus Lepraria from maritime and continental Antarctica collected in 1986–2007 was studied. Four species were distinguished, L. alpina, L. caerulescens, L. straminea and one putative new taxon provisionally called Lepraria sp. AO. L. caerulescens is tentatively resurrected from the synonyms of L. alpina for the chemotype with atranorin and angardianic/roccellic acid. Lepraria sp. AO is characterized by its granular thallus similar to other members of the L. neglecta group and the presence of two fatty acids, so far unidentified and not known from other members of the genus. Morphological and chemical diagnostic characters of all taxa, their distribution and ecological features are discussed. An updated key for identification of all Antarctic species is provided.     

Phenotypic diversity and antibiotic resistance in soil bacterial communities

The community structure in two different agricultural soils has been investigated. Phenotypic diversity was assessed by applying BIOLOG-profiles on a total of 208 bacterial isolates. Diversity indices were calculated from cluster analysis of the BIOLOG data. The bacterial isolates were also evaluated for resistance towards six different antibiotics, mercury resistance and the presence of plasmids. The presence of tetracycline-resistant determinants class A to E among Gram-negative bacteria was analysed with DNA probes. The distribution of tetracycline resistance markers among colonies growing on non-selective and tetracycline-selective plates were compared. The phenotypic approach demonstrated some difference in the diversity within the two soils. The frequency of antibiotic resistance isolates was high in both soils, whereas the frequency of mercury resistance differed significantly. We found no correlation between plasmid profiles and antibiotic resistance patterns. We found all the tetracycline resistance determinants except class B, indicating that the diversity of the tetracycline resistance determinants was complex in populations of resident soil bacteria under no apparent selective pressure for the genes in question.     

Diversity, ecology and biogeography of the freshwater diatom communities from Ulu Peninsula (James Ross Island, NE Antarctic Peninsula)

The diversity, ecology and biogeography of diatoms in lakes, seepage areas and streams on the Ulu Peninsula, a large ice-free area in the northern part of James Ross Island (Weddell Sea), were studied. A diverse diatom flora of 123 taxa was observed, dominated by several Nitzschia taxa, Psammothidium papilio, Eolimna jamesrossensis, Fragilaria capucina and Fistulifera saprophila. The results from the similarity and diversity analysis suggest James Ross Island to be biogeographically positioned within the Maritime Antarctic region, yet with some affinities with the flora of Continental Antarctica, as shown by the presence of Luticola gaussii and Achnanthes taylorensis. Based on our data, James Ross Island can thus be located close to the boundary of the two main Antarctic biogeographical regions. Diatom communities present in streams and seepage areas could be clearly distinguished from those in lakes, the latter being much more species rich. Based on the multivariate analysis, conductivity and nutrients were selected as the two main environmental factors determining the diatom composition in the Ulu Peninsula lakes. The revised taxonomy of the Antarctic diatom flora induced the construction of a transfer function for water conductivity in the studied lakes that can be applied in further palaeoecological studies.