Diversity of Both the Cultivable Protease-Producing Bacteria and Their Extracellular Proteases in the Sediments of the South China Sea

Protease-producing bacteria are known to play an important role in degrading sedimentary particular organic nitrogen, and yet, their diversity and extracellular proteases remain largely unknown. In this paper, the diversity of the cultivable protease-producing bacteria and their extracellular proteases in the sediments of the South China Sea was investigated. The richness of the cultivable protease-producing bacteria reached 10⁶ cells/g in all sediment samples. Analysis of the 16S rRNA gene sequences revealed that the predominant cultivated protease-producing bacteria are Gammaproteobacteria affiliated with the genera Pseudoalteromonas, Alteromonas, Marinobacter, Idiomarina, Halomonas, Vibrio, Shewanella, Pseudomonas, and Rheinheimera, with Alteromonas (34.6%) and Pseudoalteromonas (28.2%) as the predominant groups. Inhibitor analysis showed that nearly all the extracellular proteases from the bacteria are serine proteases or metalloproteases. Moreover, these proteases have different hydrolytic ability to different proteins, reflecting they may belong to different kinds of serine proteases or metalloproteases. To our knowledge, this study represents the first report of the diversity of bacterial proteases in deep-sea sediments.     

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.     

Mid-Holocene skua remains from King George Island,Antarctica

Seven avian remains from Mid-Holocene strata of the southeastern coast of Potter Peninsula (King George Island: Isla 25 de Mayo, South Shetland Islands, Antarctica) are reported. They were described and assigned to the brown skua Stercorarius antarcticus lonnbergi (Aves, Laridae), a living species currently breeding in the area. The presence of penguins in the same sequence is in agreement with the current dynamics of the coastal ecosystems of Antarctica. Nowadays, penguins and skuas frequent these same environments.     

Bacterial diversity in ornithogenic soils compared to mineral soils on King George Island, Antarctica

In the Nar?bski Point area of King George Island of Antarctica, ornithogenic soils form on land under Chinstrap and Gentoo Penguin rookeries. The purpose of this study was to compare the bacterial community compositions in the gradient of contamination by penguin feces; mineral soil with no contamination, and soils with medium or high contamination. The discrimination between mineral soils and ornithogenic soils by characterization of physicochemical properties and bacterial communities was notable. Physicochemical analyses of soil properties showed enrichment of carbon and nitrogen in ornithogenic soils. Firmicutes were present abundantly in active ornithogenic soils, Bacteroidetes and Proteobacteria in a formerly active one, and several diverse phyla such as Proteobacteria, Actinobacteria, and Acidobacteria in mineral soils. Some predominant species belonging to the Firmicutes and Gammaproteobacteria may play an important role for the mineralization of nutrients in ornithogenic soils. Results of this study indicate that dominant species may play an important role in mineralization of nutrients in these ecosystems.     

Diversity of the lichenized fungi in King George Island, Antarctica, revealed by phylogenetic analysis of partial large subunit rDNA sequences

Lichens are predominant and important components of flora in the terrestrial ecosystem of Antarctica. However, relatively few researches on the phylogenetic position of Antarctic lichen-forming fungi have been accomplished. In this study, partial sequences of nuclear large subunit rDNAs from 50 Antarctic specimens were obtained and the phylogeny was reconstructed. Antarctic lichen species were distributed among 4 orders, including the monophyletic order Agyrales, paraphyletic orders Pertusariales and Teloschistales, and polyphyletic order Lecanorales. Species diversity was highest in the order Lecanorales, followed by Teloschistales and Pertusariales. Based on the phylogeny and sequence similarity analyses, it is proposed that the taxonomy of Stereocaulon alpinum, Physcia caesia, Usnea aurantiacoatra, and Cladonia species should be revised by careful examination of their phenotypic and molecular characteristics. Six species known to be endemic to Antarctica, Catillaria corymbosa, Himantormia lugubris, Leptogium puberulum, Pertusaria pertusa, Rhizoplaca aspidophora, and Umbilicaria antarctica, formed unique lineages, implying independent origins in the Antarctic area.     

Microbial mats of twenty-six lakes from Potter Peninsula,King George Island,Antarctica

The taxonomic composition and ecology of microbial mats were investigated in 26 lentic environments of Potter Peninsula (King George Island, Antarctica) during the summer of 1995/96. These have different limnological characteristics according to the location of the basins. Among the 139 algal taxa registered, 10 are new records for Antarctica. Bacillariophyceae was the dominant class in terms of species richness, followed by the Cyanobacteria and Chlorophyceae. TWINSPAN classification was used to describe six epilithic algal assemblages; Canonical Correspondence Analysis ordination showed that soluble reactive phosphorus, phytoplanktonic chlorophyll a concentration and conductivity were the main sources for the variation in the data.     

Distribution of microphytobenthic biomass in Martel Inlet,King George Island (Antarctica)

The spatial and temporal variation of microphytobenthic biomass in the nearshore zone of Martel Inlet (King George Island, Antarctica) was estimated at several sites and depths (10–60 m), during three summer periods (1996/1997, 1997/1998, 2004/2005). The mean values were inversely related to the bathymetric gradient: higher ones at 10–20 m depth (136.2 ± 112.5 mg Chl a m⁻², 261.7 ± 455.9 mg Phaeo m⁻²), intermediate at 20–30 m (55.6 ± 39.5 mg Chl a m⁻², 108.8 ± 73.0 mg Phaeo m⁻²) and lower ones at 40–60 m (22.7 ± 23.7 mg Chl a m⁻², 58.3 ± 38.9 mg Phaeo m⁻²). There was also a reduction in the Chl a/Phaeo ratio with depth, from 3.2 ± 3.2 (10–20 m) to 0.7 ± 1.0 (40–60 m), showing a higher contribution of senescent phytoplankton and/or macroalgae debris at the deeper sites and the limited light flux reaching the bottom. Horizontal differences found in the biomass throughout the inlet could not be clearly related to hydrodynamics or proximity to glaciers, but with sediment characteristics. An inter-summer variation was observed: the first summer presented the highest microphytobenthic biomass apparently related to more hydrodynamic conditions, which causes the deposition of allochthonous material.     

Breeding sites and population of seabirds on Admiralty Bay,King George Island,Antarctica

The monitoring of the status and distribution of seabird populations is necessary to understand their spatial and temporal responses to rapid climate changes occurring in the Western Antarctic Peninsula area. We surveyed and mapped Admiralty Bay bird communities and related them to climate variables—temperature, temperature anomaly, Antarctic Oscillation Index and El-Niño Southern Oscillation Index. We recorded 13 breeding seabird species over three seasons (2009/2010, 2010/2011 and 2011/2012) and mapped 10 of them over an area of 149.5 ha. The ice-free areas with the greatest number of species were Point Thomas, Keller Peninsula and Hennequin Point. The most abundant species was the Adelie Penguin (Pygoscelis adeliae) followed by the Chinstrap Penguin (P. antarcticus). We observed that the number of breeding pairs of Gentoo Penguins (P. papua), Chinstrap Penguins and skuas (Catharacta maccormicki and C. antarctica) are related to temperature, temperature anomaly and El-Niño Southern Oscillation Index. The size of breeding populations and their distributions have been fluctuating over the last 30 years in ice-free areas of Admiralty Bay. Most species showed a decreasing trend from 1978 to 2012, with the exception of Chinstrap Penguins, Southern Giant Petrels (Macronectes giganteus) and skuas, which seem to be stable in numbers in the last two decades. Decreases in seabird populations from the Antarctic Peninsula are widely recognized as a response to environmental change and anthropogenic influences such as tourism and building activities, thus highlighting the importance of monitoring to support mitigation measures.     

Epilithic biomass in an outflow stream at Potter Peninsula, King George Island, Antarctica

The epilithic biomass of an outflow stream at Potter Peninsula (King George Island, Antarctica) was studied from November 1996 to February 1997 by means of chlorophyll a concentration, dry weight and ash-free dry weight. The Autotrophic Index and the Lakatos classification were also used in order to characterize the epilithic community. Several physical and chemical parameters were analyzed. Snow and ice melt greatly increased water flow through Tres Hermanos Lake and in the stream. Chlorophyll a concentrations fluctuated between undetectable and 3.5 μg cm⁻² with a marked increase, which averaged 3 orders of magnitude, towards the end of the study period. Dry weight ranged between 299.9 and 13,118.7 μg cm⁻² and ash-free dry weight between 70.8 and 996.9 μg cm⁻². According to the Autotrophic Index and the Lakatos classification, the epilithon of the stream had a low mass with low organic component and large amount of inorganic sediment. The organic matter comprised a low proportion of chlorophyll a and a major proportion of probably detritus or bacteria, rather than fauna. Accepted: 3 June 2000     

Diversity and distribution of cultivable fungi present in acid sulphate soils in chronosequence under para-periglacial conditions in King George Island,Antarctica

Extremophiles - We recovered 85 fungal isolates from the acid sulphate soils in chronosequence under para-periglacial conditions in King George Island, Antarctica. Thirty-two taxa belonging to the...     

Fish of Admiralty Bay (King George Island,South Shetland Islands,Antarctica)

Summary The species composition of the ichthyofauna of Admiralty Bay, King George Island was determined from results of sampling using bottom trawls, gill-nets and long-lines. Thirty-five species from 24 genera and 10 families (Table 1) were found. The number of species increased with depth (e.g. 7 species at 100 m, 14 species at 255 m and 21 species at 540 m), a tendency characteristic of Antarctic waters. In the bay, the catch rate obtained with a bottom trawl (greater than 30 kg/h) was roughly ten times lower than the catch rate using the same gear on the shelf around the Island. Notothenia gibberifrons was the dominant species in all trawls. The majority of these fish (about 95%) were immature juveniles (Table 4). Younger fish were found to inhabit shallower waters (Fig. 1). The majority of the fish of species Notothenia coriiceps neglecta, Notothenia rossii marmorata, Notothenia nudifrons, Trematomus newnesi and Trematomus bernacchii preferred waters about 255 m deep. Fourteen specimens of a previously undescribed species of the genus Psilodraco (currently being described by H. DeWitt) were caught in the bay within the 146 to 540 m depth range. The rare zoarcid, Lycenchelys aratrirostris, was also caught in Admirality Bay; previously this species had only been reported from the Elephant Island region. In the case of Trematomus newnesi, the occurrence of scales in the interorbital space was noted (Fig. 2), an observation which verifies this feature as a distinct taxonomical criterion for this species.     

Antioxidant activity of polar lichens from King George Island (Antarctica)

Antioxidant agents prevent reactive oxygen species, which can cause degenerative diseases. Natural antioxidants are preferred over many synthetic antioxidants, which can be toxic, for therapeutic applications. Five lichen species were collected from King George Island, Antarctica. Antioxidant activities as assessed by DPPH (1,1-diphenyl-2-picrylhydrazyl) free radical and ABTS^•+ [2,2’-azinobis-(3-ethylbenzothiazoline-6-sulfonate)] radical scavenging capacities were determined and compared with those of commercial standards BHA (butylated hydroxyanisole) and trolox [(±)-6-hydroxy-2,5,7,8-tetramethylchromane-2-carboxylic acid]. The results indicated that two lichens exhibited comparatively high antioxidant activities with the remaining three exhibiting less activity. The antioxidant activity was concentration-dependent. When compared, the antioxidant activity of crude extracts from polar lichens to previously published data for tropical and temperate lichen species, we concluded that lichens of Antarctic origin may be the potent sources of strong antioxidant agents. Such species should be explored as novel sources of effective antioxidant metabolites.     

Culturable bacteria community development in postglacial soils of Ecology Glacier, King George Island, Antarctica

Glacier forelands are excellent sites in which to study microbial succession because conditions change rapidly in the emerging soil. Development of the bacterial community was studied along two transects on lateral moraines of Ecology Glacier, King George Island, by culture-dependent and culture-independent approaches (denaturating gradient gel electrophoresis). Environmental conditions such as cryoturbation and soil composition affected both abundance and phylogenetic diversity of bacterial communities. Microbiocenosis structure along transect 1 (severe cryoturbation) differed markedly from that along transect 2 (minor cryoturbation). Soil physical and chemical factors changed along the chronosequence (time since exposure) and influenced the taxonomic diversity of cultivated bacteria, particularly along transect 2. Arthrobacter spp. played a pioneer role and were present in all soil samples, but were most abundant along transect 1. Cultivated bacteria isolated from transect 2 were taxonomically more diverse than those cultivated from transect 1; those from transect 1 tended to express a broader range of enzyme and assimilation activities. Our data suggest that cryoturbation is a major factor in controlling bacterial community development in postglacial soils, shed light on microbial succession in glacier forelands, and add a new parameter to models that describe succession phenomena.     

Phylotype diversity in a benthic cyanobacterial mat community on King George Island, maritime Antarctica

Cyanobacterial 16S ribosomal RNA gene diversity was examined in a benthic mat on Fildes Peninsula of King George Island (62o09′54.4′′S, 58o57′20.9′′W), maritime Antarctica. Environmental DNA was isolated from the mat, a clone library of PCR-amplified 16S rRNA gene fragments was prepared, and amplified ribosomal DNA restriction analysis (ARDRA) was done to assign clones to seven groups. Low cyanobacterial diversity in the mat was suggested in that 83% of the clones were represented by one ARDRA group. DNA sequences from this group had high similarity with 16S rRNA genes of Tychonema bourrellyi and T. bornetii isolates, whose geographic origins were southern Norway and Northern Ireland. Cyanobacterial morphotypes corresponding to Tychonema have not been reported in Antarctica, however, this morphotype was previously found at Ward Hunt Lake (83oN), and in western Europe (52oN). DNA sequences of three of the ARDRA groups had highest similarity with 16S rDNA sequences of the Tychonema group accounting for 9.4% of the clones. Sequences of the remaining three groups (7.6%) had highest similarity with 16S rRNA genes of uncultured cyanobacteria clones from benthic mats of Lake Fryxell and fresh meltwater on the McMurdo Ice Shelf.     

Benthic faunal associations on soft substrates at Potter Cove, King George Island, Antarctica

Associations of benthic invertebrates from Potter Cove (Antarctica) were defined from photo-transects. Density, percentage cover, species richness S′, diversity index H′, evenness index J′ and mean-size estimations were studied in relation to water depth down to 30 m. A clear bathymetric pattern was evident, with two different communities at 15 and 30 m, and a transition area between 20 and 25 m. At 15 m we observed a small number of taxa (nine in total), a high percentage of bare substratum (95%), and the dominant species were pennatulids and the bivalve Laternula elliptica. From 20 to 30 m the dominant species was the ascidian Molgula pedunculata and there was a slight increase in S′, H′ and J′, as well as in the mean size of individuals, especially in M. pedunculata, while the proportion of bare substratum showed a constant decrease with depth. Using multivariate analyses, three faunal assemblages related to depth were defined and a strong association of some species, mainly predators and opportunistic necrophages, with M. pedunculata was revealed. Ice impact (icebergs and anchor ice) seems to be the major regulating factor of benthic assemblages in shallow waters. Received: 28 April 1997 / Accepted: 17 August 1997     

Preliminary study of the soil nematode community at Machu Picchu Station, King George Island, Antarctica

We studied the distribution and abundance of nematodes in one of the most extreme terrestrial environments in the world, at Machu Picchu, King George Island, off the coast of Admiralty Bay, Antarctica. We can report that the nematode community structure under the two most common plant covers was composed of three to four species. These species were found to belong functionally to microbial and omnivore/predator feeding types. Abundances of each of the nematode species were found to be negatively correlated to soil water content, generally decreasing their abundance with increasing soil water content. The results of this study demonstrate the importance of moisture availability to the nematode community and its species composition in this Antarctic soil ecosystem.     

Expressed sequence tag analysis of Antarctic hairgrass Deschampsia antarctica from King George Island, Antarctica

Deschampsia antarctica is the only monocot that thrives in the tough conditions of the Antarctic region. It is an invaluable resource for the identification of genes associated with tolerance to various environmental pressures. In order to identify genes that are differentially regulated between greenhouse-grown and Antarctic field-grown plants, we initiated a detailed gene expression analysis. Antarctic plants were collected and greenhouse plants served as controls. Two different cDNA libraries were constructed with these plants. A total of 2,112 cDNA clones was sequenced and grouped into 1,199 unigene clusters consisting of 243 consensus and 956 singleton sequences. Using similarity searches against several public databases, we constructed a functional classification of the ESTs into categories such as genes related to responses to stimuli, as well as photosynthesis and metabolism. Real-time PCR analysis of various stress responsive genes revealed different patterns of regulation in the different environments, suggesting that these genes are involved in responses to specific environmental factors.     

Molecular diversity of microbial eukaryotes in sea water from Fildes Peninsula,King George Island,Antarctica

Data on Antarctic coastal sites remain scarce and are generally limited to microscopy; the diversity of coastal Antarctic ecosystems has long been underestimated. The diatom-dominant community in the coastal sea waters of the Fildes Peninsula has been described according to traditional protocols. Molecular diversity of microbial eukaryotes (≤20 µm) from Great Wall Cove and Ardley Cove, Fildes Peninsula, has been determined by Illumina MiSeq2000 sequencing. Inferred metabolisms of summer phytoplankton in the two coves are characterised by autotrophy and heterotrophy. The frequent occurrence of such nanoflagellates as dinoflagellates, Cryptophyta, Stramenopiles, Pyramimonas, Telonema, and Cryothecomonas is predicted to be important in these Antarctic coastal communities. Sea water exchange exists between the two coves when high tide occurs, indicating that there appears to be mixing between the microbial communities in the two coves. Cluster analysis of the microbial eukaryote composition at the phylum and genus levels reveals a conservation of the community composition between the two coves. The inner stations of Great Wall Cove represented by three shoal samples (G1, G2, and G3) are clustered closely together, surrounded by islands and formed into a semi-closed body of water. The samples from the outer stations G4 and G5 of Great Wall Cove, which are separated from the other three Great Wall stations, are more similar to the Ardley Cove samples. Sea water exchange between the outer basins might be the effect of their community compositions. The nanoplankton diversity in Great Wall Cove is richer than in Ardley Cove, according to the α-diversity index.     

Prey size selectivity by kelp gulls on Antarctic limpets at King George Island, Antarctica

The present study was performed at Potter Peninsula (King George Island, Antarctica) with the following goals: (1) to assess the size selection of kelp gulls on Antarctic limpets during the chick-rearing period, and (2) to evaluate the degree of accuracy in the use of populational abundance and size-frequency distribution as an indicator of prey availability. The average size of limpets available to kelp gulls was significantly smaller than that of the population as a whole and those actually consumed by gulls. The odds ratio revealed a strong selectivity for large limpets, when available and consumed sizes were compared. However, only a proportion of the limpets present was available to gulls. These differences clearly show that using abundance information as an indicator of a resource importance can lead to substantial errors in ecological interpretations. Accepted: 21 November 1998