Pseudomonas syringae on Plants in Iceland Has Likely Evolved for Several Million Years Outside the Reach of Processes That Mix This Bacterial Complex across Earth's Temperate Zones.

Here we report, for the first time, the occurrence of the bacteria from the species complex Pseudomonas syringae in Iceland. We isolated this bacterium from 35 of the 38 samples of angiosperms, moss, ferns and leaf litter collected across the island from five habitat categories (boreal heath, forest, subalpine and glacial scrub, grazed pasture, lava field). The culturable populations of P. syringae on these plants varied in size across 6 orders of magnitude, were as dense as 107 cfu g-1 and were composed of strains in phylogroups 1, 2, 4, 6, 7, 10 and 13. P. syringae densities were significantly greatest on monocots compared to those on dicots and mosses and were about two orders of magnitude greater in grazed pastures compared to all other habitats. The phylogenetic diversity of 609 strains of P. syringae from Iceland was compared to that of 933 reference strains of P. syringae from crops and environmental reservoirs collected from 27 other countries based on a 343 bp sequence of the citrate synthase (cts) housekeeping gene. Whereas there were examples of identical cts sequences across multiple countries and continents among the reference strains indicating mixing among these countries and continents, the Icelandic strains grouped into monophyletic lineages that were unique compared to all of the reference strains. Based on estimates of the time of divergence of the Icelandic genetic lineages of P. syringae, the geological, botanical and land use history of Iceland, and atmospheric circulation patterns, we propose scenarios whereby it would be feasible for P. syringae to have evolved outside the reach of processes that tend to mix this bacterial complex across the planet elsewhere.

Selective isolation of potentially phosphate-mobilizing, biosurfactant-producing and biodegradative bacteria associated with a sub-Arctic, terricolous lichen, Peltigera membranacea.

Lichens are the symbiotic association of fungi and a photosynthetic partner. However, non-phototrophic bacteria are also present and thought to comprise an essential part of the lichen symbiosis, although their roles in the symbiosis are still poorly understood. In this study, we isolated and characterized 110 non-phototrophic bacterial lichen associates from thalli of the terricolous lichen Peltigera membranacea The biodegradative and other nutrient-scavenging properties studied among selected isolates were phosphate mobilization, biosurfactant production and degradation of napthalene and several biopolymers, suggesting organic and inorganic nutrient scavenging as roles for bacteria in the lichen symbiotic association. Identification by partial 16S rRNA gene sequencing revealed that the isolates comprised 18 genera within the Proteobacteria, Actinobacteria, Bacteroidetes and Firmicutes, many with high similarities with bacteria typically associated with the plant and rhizosphere environments, could suggest that plants may be important sources of terricolous lichen-associated bacteria, or vice versa.

Analysis of the Peltigera membranacea metagenome indicates that lichen-associated bacteria are involved in phosphate solubilization.

Although lichens are generally described as mutualistic symbioses of fungi and photosynthetic partners, they also harbour a diverse non-phototrophic microbiota, which is now regarded as a significant part of the symbiosis. However, the role of the non-phototrophic microbiota within the lichen is still poorly known, although possible functions have been suggested, including phosphate solubilization and various lytic activities. In the present study we focus on the bacterial biota associated with the foliose lichen Peltigera membranacea. To address our hypotheses on possible roles of the non-phototrophic microbiota, we used a metagenomic approach. A DNA library of bacterial sequence contigs was constructed from the lichen thallus material and the bacterial microbiota DNA sequence was analysed in terms of phylogenetic diversity and functional gene composition. Analysis of about 30,000 such bacterial contigs from the P. membranacea metagenome revealed significant representation of several genes involved in phosphate solubilization and biopolymer degradation.

Novel bacteria associated with Arctic seashore lichens have potential roles in nutrient scavenging.

While generally described as a bipartite mutualistic association between fungi and algae or cyanobacteria, lichens also host diverse and heretofore little explored communities of nonphototrophic endolichenic bacteria. The composition and possible roles of these bacterial communities in the lichen symbiotic association constitute an emerging field of research. Saxicolous (rock-dwelling) seashore lichens present an unusual environment, characterized by rapid fluctuations in temperature, salinity, exposure to solar radiation, etc. The present study focuses on the bacterial biota associated with 4 species of crustose, halophilic, saxicolous seashore lichens found in northern Iceland. A denaturing gradient gel electrophoresis based characterization of the composition of the lichen-associated microbiotas indicated that they are markedly lichen-species-specific and clearly distinguishable from the environmental microbiota represented by control sampling. A collection of bacterial strains was investigated and partially identified by 16S rDNA sequencing. The strains were found to belong to 7 classes: Alphaproteobacteria, Bacilli, Actinobacteria, Flavobacteria, Cytophagia, Sphingobacteria, and Gammaproteobacteria. Several isolates display only a modest level of similarity to their nearest relatives found in GenBank, suggesting that they comprise previously undescribed taxa. Selected strains were tested for inorganic phosphate solubilization and biodegradation of several biopolymers, such as barley ß-glucan, xylan, chitosan, and lignin. The results support a nutrient-scavenging role of the associate microbiota in the seashore lichen symbiotic association.

Effect of various factors on ethanol yields from lignocellulosic biomass by Thermoanaerobacterium AK17.

The ethanol production capacity from sugars and lignocellulosic biomass hydrolysates (HL) by Thermoanaerobacterium strain AK(17) was studied in batch cultures. The strain converts various carbohydrates to, acetate, ethanol, hydrogen, and carbon dioxide. Ethanol yields on glucose and xylose were 1.5 and 1.1 mol/mol sugars, respectively. Increased initial glucose concentration inhibited glucose degradation and end product formation leveled off at 30 mM concentrations. Ethanol production from 5 g L(-1) of complex biomass HL (grass, hemp, wheat straw, newspaper, and cellulose) (Whatman paper) pretreated with acid (0.50% H(2) SO(4)), base (0.50% NaOH), and without acid/base (control) and the enzymes Celluclast and Novozyme 188 (0.1 mL g(-1) dw; 70 and 25 U g(-1) of Celluclast and Novozyme 188, respectively) was investigated. Highest ethanol yields (43.0 mM) were obtained on cellulose but lowest on hemp leafs (3.6 mM). Chemical pretreatment increased ethanol yields substantially from lignocellulosic biomass but not from cellulose. The influence of various factors (HL, enzyme, and acid/alkaline concentrations) on end-product formation from 5 g L(-1) of grass and cellulose was further studied to optimize ethanol production. Highest ethanol yields (5.5 and 8.6 mM ethanol g(-1) grass and cellulose, respectively) were obtained at very low HL concentrations (2.5 g L(-1)); with 0.25% acid/alkali (v/v) and 0.1 mL g(-1) enzyme concentrations. Inhibitory effects of furfural and hydroxymethylfurfural during glucose fermentation, revealed a total inhibition in end product formation from glucose at 4 and 6 g L(-1), respectively.