Agarolytic culturable bacteria associated with three antarctic subtidal macroalgae

Bacterial communities of Antarctic marine macroalgae remain largely underexplored in terms of diversity and biotechnological applications. In this study, three Antarctic subtidal macroalgae (Himantothallus grandifolius, Pantoneura plocamioides and Plocamium cartilagineum), two of them endemic of Antarctica, were investigated as a source for isolation of agar-degrading bacteria. A total of 21 epiphytic isolates showed agarolytic activity at low temperature on agar plates containing agar as the sole carbon source. 16S rRNA identification showed that the agar-degrading bacteria belonged to the genera Cellulophaga, Colwellia, Lacinutrix, Olleya, Paraglaciecola, Pseudoalteromonas and Winogradskyella. The agarase enzyme from a potential new species of the genus Olleya was selected for further purification. The enzyme was purified from the culture supernatant of Olleya sp. HG G5.3 by ammonium sulfate precipitation and ion-exchange chromatography. Molecular weight of the agarase was estimated to be 38 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The purified enzyme exhibited activity at 4 °C, retaining >?50% of its maximum activity at this temperature. This is the first study reporting the phylogeny of agar-degrading bacteria isolated from Antarctic subtidal macroalgae and the results suggest the huge potential of Antarctic algae-associated bacteria as a source of cold-active hydrolytic enzymes of biotechnological interest.     

A comparison of epiphytic diatom communities on <Emphasis Type="Italic">Plocamium cartilagineum</Emphasis> (Plocamiales,Florideophyceae) from two Antarctic areas

Our understanding of diatoms, one of the most important Antarctic primary producers, is based mostly on investigations of plankton, sea-ice, and sediment samples. Herein, we contribute to the limited research devoted to benthic Antarctic diatoms by presenting a study on epiphytic diatom communities sampled in two remote Antarctic regions: Admiralty Bay (maritime Antarctica, Antarctic Peninsula) and Terra Nova Bay (Ross Sea). Recent studies have demonstrated that the most critical factor for the local epiphytic diatom communities was the nature of the substrate. In order to eliminate this factor so we could evaluate other potential controls, we sampled epiphytic diatoms from only one substrate that is common to both regions: the macroalgae Plocamium cartilagineum (L.) Dixon. Thalli of P. cartilagineum and their associated microalgal community was collected in January 2011 (Admiralty Bay) and 2012 (Terra Nova Bay) from a water depth of 5–25 m. Dehydrated macroalgal pieces were placed on stubs and sputter-coated, which allowed observation of diatoms attached to the substrate in their original position using scanning electron microscopy. A total of 72 taxa were observed, of which 31 taxa were common to both regions. Cell abundance and diatom growth form dominance were significantly different in Admiralty Bay and Terra Nova Bay samples. Total diatom abundance was higher in Admiralty Bay samples, dominated by adnate diatoms (Cocconeis spp.), but the number of taxa found as well as the values of ecological indices were higher for samples from the Ross Sea, where motile forms were dominant (Navicula spp.). Our results suggest that Antarctic shallow-water benthic habitats may present a high degree of microniche heterogeneity and highlight the need of fine-scale analyses in microbial studies. We also suggest grazers as a factor that contributes greatly to the observed differences.     

Changes in the microbial community during repeated anaerobic microbial dechlorination of pentachlorophenol

Pentachlorophenol (PCP) has been widely used as a pesticide in paddy fields and has imposed negative ecological effect on agricultural soil systems, which are in typically anaerobic conditions. In this study, we investigated the effect of repeated additions of PCP to paddy soil on the microbial communities under anoxic conditions. Acetate was added as the carbon source to induce and accelerate cycles of the PCP degradation. A maximum degradation rate occurred at the 11th cycle, which completely transformed 32.3 μM (8.6 mg L^?1) PCP in 5 days. Illumina high throughput sequencing of 16S rRNA gene was used to profile the diversity and abundance of microbial communities at each interval and the results showed that the phyla of Bacteroidates, Firmicutes, Proteobacteria, and Euryarchaeota had a dominant presence in the PCP-dechlorinating cultures. Methanosarcina, Syntrophobotulus, Anaeromusa, Zoogloea, Treponema, W22 (family of Cloacamonaceae), and unclassified Cloacamonales were found to be the dominant genera during PCP dechlorination with acetate. The microbial community structure became relatively stable as cycles increased. Treponema, W22, and unclassified Cloacamonales were firstly observed to be associated with PCP dechlorination in the present study. Methanosarcina that have been isolated or identified in PCP dechlorination cultures previously was apparently enriched in the PCP dechlorination cultures. Additionally, the iron-cycling bacteria Syntrophobotulus, Anaeromusa, and Zoogloea were enriched in the PCP dechlorination cultures indicated they were likely to play an important role in PCP dechlorination. These findings increase our understanding for the microbial and geochemical interactions inherent in the transformation of organic contaminants from iron rich soil, and further extend our knowledge of the PCP-transforming microbial communities in anaerobic soil conditions.     

Extracellular lipase from <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> JCM5962(T): Isolation,identification, and characterization

The study was done to isolate, identify, and characterize a good lipolytic strain from soil. Lipolytic strain isolation was done using tributyrin agar medium. The biochemical testing and 16S rRNA gene sequencing analysis was done for identification. The enzyme was purified using ammonium sulfate precipitation and column chromatography. Results have shown a novel high lipolytic strain of P. aeruginosa JCM5962(T), isolated from soil of sugarcane field. The 16S rRNA sequence analysis confirmed the strain as P. aeruginosa JCM5962(T); further, the sequence was submitted to Genbank (KX946966.1). The isolate produced an extracellular lipase which was purified as single band of 31 kDa. Maximum lipase activity was observed at 50 °C and pH 8.0. Activity was enhanced in the presence of cobalt and benzene solvent, whereas mercury, sodium dodecyl sulfate, and chloroform inhibited it. The enzyme’s marked stability and activity at high temperature, alkaline pH and organic solvents suggest that this can be effectively used in a variety of applications in industries and as biotechnological tools.     

Linkages of <Emphasis Type="Italic">Firmicutes</Emphasis> and <Emphasis Type="Italic">Bacteroidetes</Emphasis> populations to methanogenic process performance

To identify potential linkages between specific bacterial populations and process performance in anaerobic digestion, the dynamics of bacterial community structure was monitored with high-throughput sequencing in triplicate anaerobic digesters treating animal waste. Firmicutes and Bacteroidetes were found as the two most abundant populations, however, with contrasting population dynamics in response to organic overloading. Firmicutes dominated the bacterial community during stable process performance at low organic loading rate, representing over 50 % of the bacterial abundance. In contrast, the onset of organic overloading raised the relative abundance of Bacteroidetes from 20 ± 2.6 to 44 ± 3.1 %. In addition to the significant negative correlation between the relative abundance of Firmicutes and Bacteroidetes, populations of Firmicutes and Bacteroidetes were found to be linked to process parameters including organic loading rate, volatile fatty acids concentration, and methane production. Therefore, the population abundance ratio of Firmicutes to Bacteroidetes (F/B ratio) was suggested as a potential indicator for process performance. The interactions between Firmicutes and Bacteroidetes populations could be exploited to develop strategies for the prevention of performance perturbation in anaerobic digestion processes.     

Competition between native Antarctic vascular plants and invasive <Emphasis Type="Italic">Poa annua</Emphasis> changes with temperature and soil nitrogen availability

Over the last decades human have introduced non-native organisms to Antarctica, including the grass species Poa annua. This non-native grass under constant growth temperatures has been shown negatively affect the growth of the only two native Antarctic vascular plants, Deschampsia antarctica and Colobanthus quitensis, under constant growth temperatures. However, whether there are changes in the interaction between these species under warmer conditions is an important question. In cold ecosystems, soil nutrient status directly affects plant responses to increases in temperature and Antarctic soils are highly variable in nutrient supply. Thus, in this study we experimentally assessed the interaction between the non-native Poa with the two native Antarctic vascular plant species at two different temperatures and levels of nutrient availability. Individual mats of the study species were collected in King George Island, and then transported to Concepcion where we conducted competition experiments. In the first experiment we used soil similar to that of Antarctica and plants in competition were grown at two temperatures: 5°/2° and 11°/5 °C (day/night temperature). In a second experiment plants were grown in these two temperature regimes, but we varied nitrogen (N) availability by irrigating plants with Hoagland solutions that contained 8000 or 300 µM of N. Overall, Poa exerted a competitive effect on Deschampsia but only at the higher temperature and higher N availability. At 5°/11 °C the competitive response of Deschampsia to Poa was of similar magnitude to the competitive effect of P. Deschampsia, and the competitive effect was greater with at low N. The competitive effect of Poa was similar to the competitive response of Colobanthus to Poa at both temperatures and N levels. Thus, at low temperatures and N soil content the native Antarctic species might withstand Poa invasion, but this might change with climate warming.     

Seasonal and altitudinal changes of culturable bacterial and yeast diversity in Alpine forest soils

The effect of altitude and season on abundance and diversity of the culturable heterotrophic bacterial and yeast community was examined at four forest sites in the Italian Alps along an altitude gradient (545–2000 m). Independently of altitude, bacteria isolated at 0 °C (psychrophiles) were less numerous than those recovered at 20 °C. In autumn, psychrophilic bacterial population increased with altitude. The 1194 bacterial strains were primarily affiliated with the classes Alpha-, Beta-, Gammaproteobacteria, Spingobacteriia and Flavobacteriia. Fifty-seven of 112 operational taxonomic units represented potential novel species. Strains isolated at 20 °C had a higher diversity and showed similarities in taxa composition and abundance, regardless of altitude or season, while strains isolated at 0 °C showed differences in community composition at lower and higher altitudes. In contrast to bacteria, yeast diversity was season-dependent: site- and altitude-specific effects on yeast diversity were only detected in spring. Isolation temperature affected the relative proportions of yeast genera. Isolations recovered 719 strains, belonging to the classes Dothideomycetes, Saccharomycetes, Tremellomycetes and Mycrobotryomycetes. The presence of few dominant bacterial OTUs and yeast species indicated a resilient microbial population that is not affected by season or altitude. Soil nutrient contents influenced significantly abundance and diversity of culturable bacteria, but not of culturable yeasts.     

Psychrotolerant <Emphasis Type="Italic">Sphingobacterium kitahiroshimense</Emphasis> LT-2 Isolated from Dhundi Glacier,Himachal Pradesh: Origin Prediction and Future Application

A psychrotolerant bacterium, isolated from Dhundi Glacier, Himachal Pradesh (India) was identified as Sphingobacterium kitahiroshimense LT-2 on the basis of biochemical, molecular and phylogenetic analysis. Sphingobacterium kitahiroshimense was first reported from Japan and was isolated from the city of Kitahiroshima, Hokkaido, Japan. In this report we have discussed about the origin of our strain and predicted that air masses and dust associated microbial cells transportation phenomena may be applicable for the origin of this species in this region. Enzymes and secondary metabolites secreted by the genus Sphingobacterium have enormous potentiality regarding their biotechnological application. Preliminary study of our strain based on metabolic profiling through HPLC showed many new metabolites were secreted by the bacterium when grown in presence of different sugar medium at 28 °C. As far as our knowledge this is the first report about Sphingobacterium species isolated from this region. This preliminary finding will help to draw an idea about the bacterial population in this Himalayan Glaciers (in HP) as well as biotechnological application of this strain can be explored further.     

A novel thermostable and organic solvent-tolerant lipase from <Emphasis Type="Italic">Xanthomonas oryzae</Emphasis> pv. <Emphasis Type="Italic">oryzae</Emphasis> YB103: screening,purification and characterization

Thermostable lipases offer major biotechnological advantages over mesophilic lipases. In this study, an intracellular thermostable and organic solvent-tolerant lipase-producing strain YB103 was isolated from soil samples and identified taxonomically as Xanthomonas oryzae pv. oryzae. The lipase from X. oryzae pv. oryzae YB103 (LipXO) was purified 101.1-fold to homogeneity with a specific activity of 373.9 U/mg. The purified lipase showed excellent thermostability, exhibiting 51.1 % of its residual activity after incubation for 3 days at 70 °C. The enzyme showed optimal activity at 70 °C, suggesting it is a thermostable lipase. LipXO retained 75.1–154.1 % of its original activity after incubation in 20 % (v/v) hydrophobic organic solvents at 70 °C for 24 h. Furthermore, LipXO displayed excellent stereoselectivity (e.e._p >99 %) toward (S)-1-phenethyl alcohol in n-hexane. These unique properties of LipXO make it promising as a biocatalyst for industrial processes.     

Yeasts from sub-Antarctic region: biodiversity,enzymatic activities and their potential as oleaginous microorganisms

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. Sixty-one yeasts strains were isolated from King George Island, Antarctica which were characterized physiologically and identified at the molecular level using the D1/D2 region of rDNA. Fifty-eight yeasts (belonging to the genera Cryptococcus, Leucosporidiella, Rhodotorula, Guehomyces, Candida, Metschnikowia and Debaryomyces) were screened for extracellular amylolytic, proteolytic, esterasic, pectinolytic, inulolytic xylanolytic and cellulolytic activities at low and moderate temperatures. Esterase activity was the most common enzymatic activity expressed by the yeast isolates regardless the assay temperature and inulinase was the second most common enzymatic activity. No cellulolytic activity was detected. One yeast identified as Guehomyces pullulans (8E) showed significant activity across six of seven enzymes types tested. Twenty-eight yeast isolates were classified as oleaginous, being the isolate 8E the strain that accumulated the highest levels of saponifiable lipids (42 %).     

Agar-degrading bacteria isolated from Antarctic macroalgae

This study describes the taxonomic diversity of pigmented, agar-degrading bacteria isolated from the surface of macroalgae collected in King George Island, Antarctica. A total of 30 pigmented, agarolytic bacteria were isolated from the surface of the Antarctic macroalgae Adenocystis utricularis, Monostroma hariotii, Iridaea cordata, and Pantoneura plocamioides. Based on the 16S rRNA data, the agarolytic isolates were affiliated to the genera Algibacter, Arthrobacter, Brachybacterium, Cellulophaga, Citricoccus, Labedella, Microbacterium, Micrococcus, Salinibacterium, Sanguibacter, and Zobellia. Isolates phylogenetically related to Cellulophaga algicola showed the highest agarase activity in culture supernatants when tested at 4 and 37 °C. This is the first investigation of pigmented agar-degrading bacteria, members of microbial communities associated with Antarctic macroalgae, and the results suggest that they represent a potential source of cold-adapted agarases of possible biotechnological interest.     

Comparison of microbial communities during the anaerobic digestion of <Emphasis Type="Italic">Gracilaria</Emphasis> under mesophilic and thermophilic conditions

Mesophilic and thermophilic anaerobic digesters (MD and TD, respectively) utilizing Gracilaria and marine sediment as the substrate and inoculum, respectively, were compared by analyzing their performances and microbial community changes. During three successive transfers, the average cumulative methane yields in the MD and TD were 222.6 ± 17.3 mL CH₄/g volatile solids (VS) and 246.1 ± 11 mL CH₄/g VS, respectively. The higher hydrolysis rate and acidogenesis in the TD resulted in a several fold greater accumulation of volatile fatty acids (acetate, propionate, and butyrate) followed by a larger pH drop with a prolonged recovery than in the MD. However, the operational stability between both digesters remained comparable. Pyrosequencing analyses revealed that the MD had more complex microbial diversity indices and microbial community changes than the TD. Interestingly, Methanomassiliicoccales, the seventh methanogen order was the predominant archaeal order in the MD along with bacterial orders of Clostridiales, Bacteriodales, and Synergistales. Meanwhile, Coprothermobacter and Methanobacteriales dominated the bacterial and archaeal community in the TD, respectively. Although the methane yield is comparable, both MD and TD show a different profile of pH, VFA and the microbial communities.     

Molecular cloning and characterization of the <Emphasis Type="Italic">MsHSP17.7</Emphasis> gene from <Emphasis Type="Italic">Medicago sativa</Emphasis> L.

Heat shock proteins (HSPs) are ubiquitous protective proteins that play crucial roles in plant development and adaptation to stress, and the aim of this study is to characterize the HSP gene in alfalfa. Here we isolated a small heat shock protein gene (MsHSP17.7) from alfalfa by homology-based cloning. MsHSP17.7 contains a 477-bp open reading frame and encodes a protein of 17.70-kDa. The amino acid sequence shares high identity with MtHSP (93.98 %), PsHSP17.1 (83.13 %), GmHSP17.9 (74.10 %) and SlHSP17.6 (79.25 %). Phylogenetic analysis revealed that MsHSP17.7 belongs to the group of cytosolic class II small heat shock proteins (sHSP), and likely localizes to the cytoplasm. Quantitative RT-PCR indicated that MsHSP17.7 was induced by heat shock, high salinity, peroxide and drought stress. Prokaryotic expression indicated that the salt and peroxide tolerance of Escherichia coli was remarkably enhanced. Transgenic Arabidopsis plants overexpressing MsHSP17.7 exhibited increased root length of transgenic Arabidopsis lines under salt stress compared to the wild-type line. The malondialdehyde (MDA) levels in the transgenic lines were significantly lower than in wild-type, although proline levels were similar between transgenic and wild-type lines. MsHSP17.7 was induced by heat shock, high salinity, oxidative stress and drought stress. Overexpression analysis suggests that MsHSP17.7 might play a key role in response to high salinity stress.     

Water-related environments: a multistep procedure to assess the diversity and enzymatic properties of cultivable bacteria

Studying the culturable portion of environmental bacterial populations is valuable for understanding the ecology, for discovering taxonomically interesting isolates and for exploiting their enzymatic abilities. In this study, diverse water-related samples, iced water (3 °C) from river, the sediment (29 °C) and water (55 °C) of a hot-spring, were investigated by two cultivation strategies, Dry and novel Wet approach. The isolates were clustered by fluorescent internal transcribed spacer PCR and identified by 16S rRNA sequencing. Several bacterial groups were also sub-typed through the application of Random Amplified Microsatellite Polymorphisms method. A broad enzymatic screening of all bacterial isolates was performed in order to assess the proteolytic, cellulolytic, lipolytic, esterolytic, amylolytic properties, as well as catalase and peroxidase activities. The Wet cultivation demonstrated to be suitable for the isolation of potential new species belonging to genera Massilia, Algoriphagus, Rheinheimera and Pandoraea. Valuable microbial resources with extensive enzymatic activities were recognized among the psychrophilic (Pantoea brenneri and Serratia sp.), mesophilic (Pandoraea, Massilia, Pseudomonas, Stenotrophomonas, Bacillus and Aeromonas) and thermophilic bacteria (Aeribacullus pallidus and Geobacillus kaustophilus). The experimental strategy developed in this study includes simple investigation tools able to reveal the genetic and enzymatic peculiarities of isolated microorganisms. It can be applied to different kinds of aquatic samples and extreme environments similar to those described in this study.     

Medium factors on anaerobic production of rhamnolipids by <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> SG and a simplifying medium for in situ microbial enhanced oil recovery applications

Aerobic production of rhamnolipid by Pseudomonas aeruginosa was extensively studied. But effect of medium composition on anaerobic production of rhamnolipid by P. aeruginosa was unknown. A simplifying medium facilitating anaerobic production of rhamnolipid is urgently needed for in situ microbial enhanced oil recovery (MEOR). Medium factors affecting anaerobic production of rhamnolipid were investigated using P. aeruginosa SG (Genbank accession number KJ995745). Medium composition for anaerobic production of rhamnolipid by P. aeruginosa is different from that for aerobic production of rhamnolipid. Both hydrophobic substrate and organic nitrogen inhibited rhamnolipid production under anaerobic conditions. Glycerol and nitrate were the best carbon and nitrogen source. The commonly used N limitation under aerobic conditions was not conducive to rhamnolipid production under anaerobic conditions because the initial cell growth demanded enough nitrate for anaerobic respiration. But rhamnolipid was also fast accumulated under nitrogen starvation conditions. Sufficient phosphate was needed for anaerobic production of rhamnolipid. SO₄ ^2? and Mg²⁺ are required for anaerobic production of rhamnolipid. Results will contribute to isolation bacteria strains which can anaerobically produce rhamnolipid and medium optimization for anaerobic production of rhamnolipid. Based on medium optimization by response surface methodology and ions composition of reservoir formation water, a simplifying medium containing 70.3 g/l glycerol, 5.25 g/l NaNO₃, 5.49 g/l KH₂PO₄, 6.9 g/l K₂HPO₄·3H₂O and 0.40 g/l MgSO₄ was designed. Using the simplifying medium, 630 mg/l of rhamnolipid was produced by SG, and the anaerobic culture emulsified crude oil to EI₂₄ = 82.5 %. The simplifying medium was promising for in situ MEOR applications.     

Microbial communities responsible for the degradation of poly(lactic acid)/poly(3-hydroxybutyrate) blend mulches in soil burial respirometric tests

The microbial communities responsible for the degradation of poly(lactic acid)/poly(3-hydroxybutyrate) (PLA/PHB) blend foils were investigated in 1 year long laboratory soil burial experiments. Different PLA/PHB foils were tested: (a) PLA/PHB original transparent foil, (b) PLA/PHB carbon black filled foil and (c) PLA/PHB black foil previously exposed for 90 days to sun light. The microbiome diversity of these three types of foil was compared with that identified from soil/perlite sample at the beginning of experiment and that developed on a cellulose mat. Culture-dependent and culture-independent (DGGE-cloning) approaches together with PLA, PHB and PLA/PHB degradation plate assays were employed. The cultivation strategy combined with degradation tests permitted the isolation and evaluation of several PLA/PHB blend degrading microorganisms such as members of the genera Bacillus, Paenibacillus, Streptomyces, Rhodococcus, Saccharothrix, Arthrobacter, Aureobasidium, Mortierella, Absidia, Actinomucor, Bjerkandera, Fusarium, Trichoderma and Penicillium. The DGGE-cloning investigation increased the information about the microbial communities occurring during bioplastic degradation detecting several bacterial and fungal taxa and some of them (members of the orders Anaerolineales, Selenomonadales, Thelephorales and of the genera Pseudogymnoascus and Pseudeurotium) were revealed here for the first time. This survey showed the microbiome colonizing PLA/PHB blend foils and permitted the isolation of several microorganisms able to degrade the tested polymeric blends.     

The cephalopod prey of the Weddell seal, <Emphasis Type="Italic">Leptonychotes weddellii</Emphasis>, a biological sampler of the Antarctic marine ecosystem

Weddell seals, Leptonychotes weddellii, are important apex predators in the food web of the Antarctic marine ecosystem. However, detailed information on their trophic relationships with cephalopods is scarce. Moreover, cephalopods play a key role in the marine environment, but knowledge of their feeding habits is limited by lack of data. Here, we have combined the use of this seal as a biological sampler together with measurements of the stable isotopic signature of the beaks of their cephalopod prey. Thus, the aims of the present study were: (1) to examine in detail the cephalopod portion of the diet of Weddell seals by means of scat analysis and (2) to assess the habitat use and trophic level of the different cephalopod prey taxa identified. From January to February 2009, a total of 48 faecal droppings were collected at Hope Bay, Antarctic Peninsula. Cephalopods were mainly represented by beaks (n = 83) which were identified to the lowest possible taxonomic level. Furthermore, subsamples of beaks were separated for further isotopic analysis. Relative abundance of stable isotopes of carbon (δ¹³C) and nitrogen (δ¹⁵N) was determined by continuous-flow isotope-ratio mass spectrometry. Cephalopods were represented uniquely by octopods of the subfamily Eledoninae. Pareledone turqueti was the dominant prey species followed by the papillated Pareledone species group and Adelieledone polymorpha. We conclude that Weddell seals preyed primarily on benthic prey resources. Furthermore, the relatively similar δ¹³C and δ¹⁵N values in beaks of the three octopod prey taxa suggest that these share the same type of habitat and occupy similar trophic level positions.     

Degraded soil increases the performance of a dominant grass, <Emphasis Type="Italic">Andropogon gerardii</Emphasis> (Big bluestem)

Dominant grasses can suppress subordinate species in grassland restorations. Examining factors that influence performance of a dominant grass when interacting with subordinate forbs may provide insights for maintaining plant community diversity. The objective of our study was to determine how soils of different restoration ages and functionally different forbs influence the performance (using biomass and tillering rate as proxies) of a dominant grass: Andropogon gerardii. Sites included a cultivated field and two restored prairies (4 or 16 years after restoration) at Konza Prairie (NE Kansas). We hypothesized A. gerardii performance would be greater in more degraded soils and when interacting with legumes. Soil structure, nutrient status, and microbial biomass were measured in soil that was used to conduct the plant interaction study. Andropogon gerardii performance was measured during an 18-week greenhouse experiment using the relative yield index calculated from net absolute tillering rate and final biomass measurements in three soil restoration age treatments combined with four interacting forb treatments. Restoration improved soil structure, reduced plant-available nutrients, and increased microbial biomass. Relative yield index values of A. gerardii were greater with non-legumes than legumes. Andropogon gerardii performed best in degraded soils, which may explain the difficulty in restoring tallgrass prairie diversity in long-term cultivated soil. Results from this study suggest practices that promote soil aggregation and fungal biomass, coupled with including a high abundance of legumes in seed mixes could reduce dominance of A. gerardii and likely increase plant diversity in tallgrass prairie restorations.     

The Impacts of Above- and Belowground Plant Input on Soil Microbiota: Invasive <Emphasis Type="Italic">Spartina alterniflora</Emphasis> Versus Native <Emphasis Type="Italic">Phragmites australis</Emphasis>

Invasive plants affect soil food webs through various resource inputs including shoot litter, root litter and living root input. The net impact of invasive plants on soil biota has been recognized; however, the relative contributions of different resource input pathways have not been quantified. Through a 2 × 2 × 2 factorial field experiment, a pair of invasive and native plant species (Spartina alterniflora vs. Phragmites australis) was compared to determine the relative impacts of their living roots or shoots and root litter on soil microbial and nematode communities. Living root identity affected bacteria-to-fungi PLFA ratios, abundance of total nematodes, plant-feeding nematodes and omnivorous nematodes. Specifically, the plant-feeding nematodes were 627% less abundant when living roots of invasive S. alterniflora were present than those of native P. australis. Likewise, shoot and root biomass (within soil at 0–10 cm depth) of S. alterniflora was, respectively, 300 and 100% greater than those of P. australis. These findings support the enemy release hypothesis of plant invasion. Root litter identity affected other components of soil microbiota (that is, bacterial-feeding nematodes), which were 34% more abundant in the presence of root litter of P. australis than S. alterniflora. Overall, more variation associated with nematode community structure and function was explained by differences in living roots than root or shoot litter for this pair of plant species sharing a common habitat but contrasting invasion degrees. We conclude that belowground resource input is an important mechanism used by invasive plants to affect ecosystem structure and function.     

Predictive functional profiling using marker gene sequences and community diversity analyses of microbes in full-scale anaerobic sludge digesters

Anaerobic digestion (AD) is widely used in treating the sewage sludge, as it can reduce the amount of sludge, eliminate pathogens and produce biofuel. To enhance the operational performance and stability of anaerobic bioreactors, operational and conventional chemical data from full-scale sludge anaerobic digesters were collected over a 2-year period and summarized, and the microbial community diversity of the sludge sample was investigated at various stages of the AD process. For the purpose of distinguishing between the functional and community diversity of the microbes, Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) software was used to impute the prevalence of 16S rDNA marker gene sequences in the difference in various sludge samples. Meanwhile, a taxa analysis was also carried out to investigate the different sludge samples. The microbial community diversity analysis of one AD sludge sample showed that the most dominant bacterial genera were Saccharicrinis, Syntrophus, Anaerotruncus and Thermanaerothrix. Among archaea, acetoclastic Methanosaeta represented 56.0 %, and hydrogenotrophic Methanospirillum, Methanoculleus, Methanothermus and Methanolinea accounted for 41.3 % of all methanogens. The taxa, genetic and functional prediction analyses of the feedstock and AD sludge samples suggested great community diversity differences between them. The taxa of bacteria in two AD sludge samples were considerably different, but the abundances of the functional KEGG pathways took on similar levels. The numbers of identified pathogens were significantly lower in the digested sludge than in the feedstock, but the PICRUSt results showed the difference in “human diseases” abundances in the level-1 pathway between the two sludge samples was small.