Bjarne Landfald

Osmoregulation in Escherichia coli by accumulation of organic osmolytes: betaines, glutamic acid, and trehalose

It has been shown previously that externally added glycine betaine is accumulated in Escherichia coli in response to the external osmotic strength. Here we have shown, by using nuclear magnetic resonance spectroscopy and radiochemical methods, that E. coli growing in a glucose-mineral medium of elevated osmotic strength generated with NaCl, had the same capacity to accumulate proline betaine and glycine betaine. Its capacity to accumulate γ-butyrobetaine was, however, 40 to 50% lower. Accordingly, externally added proline betaine and glycine betaine stimulated aerobic growth of osmotically stressed cells equally well, and they were more osmoprotective than γ-butyrobetaine. In cells grown at an osmotic strength of 0.64, 1.01, or 1.47 osmolal, respectively, the molal cytoplasmic concentration of the two former betaines corresponded to 29, 38, or 58% of the external osmotic strength. Nuclear magnetic resonance spectroscopy revealed that trehalose and glutamic acid were the only species of organic osmolytes accumulated in significant amounts in cells grown under osmotic stress in glucosemineral medium without betaines. Their combined molal concentration in the cytoplasm of cells grown at 1.01 osmolal corresponded to 27% of the external osmotic strength.

Capsaspora owczarzaki is an independent opisthokont lineage

Abstract Transitions from unicellularity to multicellularity have occurred several times in the history of life. Two of the most conspicuous multicellular kingdoms, Metazoa and Fungi, form a monophyletic clade, known as the opisthokonts, which comprises some unicellular lineages, such as Choanoflagellata, Nucleariidae, Ichthyosporea (also known as the DRIPs or Mesomycetozoea), Ministeria and Corallochytrium [1,2]. Among these unicellular opisthokonts we should expect to find the closest extant relatives of the multicellular Metazoa and Fungi. Choanoflagellates have traditionally been considered to be closely related to metazoans [1–6] and the Ichthyosporea are proposed to be the next closest outgroup [5]. By contrast, the position of the nucleariids is controversial [7–10]. Nuclearia sp. (ATCC 30864), recently renamed as Capsaspora owczarzaki, a filose amoeboid symbiont of a pulmonate snail, has never been confidently assigned to any opisthokont lineage [7–9]. Here, we report large subunit ribosomal and actin sequences of Capsaspora owczarzaki and an actin sequence of the novel ichthyosporean species Sphaeroforma arctica [11]. We test the phylogenetic position of Capsaspora owczarzaki , and the phylogenetic position of the nucleariids within the opisthokonts.

Molecular-phylogenetic, structural and biochemical features of a cold-adapted, marine ichthyosporean near the animal-fungal divergence, described from in vitro cultures

A hitherto undescribed eukaryotic microorganism, provisionally named Sphaeroforma arctica, was isolated from the arctic marine amphipod Gammarus setosus. Phylogenetic inference based on a partial sequence of the small subunit ribosomal RNA (SSU-rRNA) gene, grouped the organism with members of the Ichthyophonida sub-clade of the recently established class Ichthyosporea. Its closest relative by SSU-rDNA analysis was Pseudoperkinsus tapetis, a Perkinsus-like clam pathogen of the Iberian peninsula. S. arctica and P. tapetis were found to share 99.3% sequence similarity. Under the in vitro growth conditions employed, the organism showed a continuous vegetative growth, manifested as steady proliferation of cells 5–7 m in diameter within a spherical wall derived from its parent cell. After approximately 48 h at 12 °C, the wall ruptured with the release of 120–150 individual cells, and the cycle was repeated. No budding, hyphal, amoeboid, sporal or flagellated growth stages were observed. The mitochondrial cristae of S. arctica were flattened. The cell wall of cells cultured in vitro was composed almost exclusively of carbohydrates, with N-acetyl-galactosamine as the major monomer, constituting close to 70% of the dry weight. Polyunsaturated fatty acids, mostly eicosapentaenoic and docosahexaenoic acid, constituted approximately 70% of total fatty acids, supporting an evolutionary adaptation to a life at permanently low temperatures. We conclude that S. arctica is a new species belonging to a new genus within the Ichthyosporea class of protists.

The microbial diversity of Polar environments is a fertile ground for bioprospecting.

The term bioprospecting has been adopted for systematic searches in nature for new bioactive compounds, genes, proteins, microorganisms and other products with potential for commercial use. Much effort has been focused on microorganisms able to thrive under harsh conditions, including the Polar environments. Both the lipid and protein cellular building blocks of Polar microorganisms are shaped by their adaptation to the permanently low temperatures. In addition, strongly differing environments, such as permafrost, glaciers and sea ice, have contributed to additional functional diversity. Emerging massive-parallel sequencing technologies have revealed the existence of a huge, hitherto unseen diversity of low-abundance phylotypes--the rare biosphere--even in the Polar environments. This realization has further strengthened the need to employ cultivation-independent approaches, including metagenomics and single-cell genomic sequencing, to get comprehensive access to the genetic diversity of microbial communities for bioprospecting purposes. In this review, we present an updated snapshot of recent findings on the molecular basis for adaptation to the cold and the phylogenetic diversities of different Polar environments. Novel approaches in bioprospecting are presented and we conclude by showing recent bioprospecting outcomes in terms of new molecules patented or applied by some biotech companies.

Influence of growth conditions on fatty acid composition of a polyunsaturated-fatty-acid-producing Vibrio species

Abstract The influence on fatty acid composition of growth medium composition and phase of growth during batch culture and of dilution rate and growth temperature during continuous culture was studied in the eicosapentaenoic-acid (20:5 n-3)-producing Vibrio CCUG 35308. In glucose-mineral medium, even-numbered normal fatty acyl residues, primarily 16:0, 16:1, 18:1, and 20:5, strongly dominated (ca. 90%), and the fatty acid profile remained practically unchanged throughout a batch-growth cycle. In nutrient broth, the contribution by “uncommon” fatty acids, mainly i-13:0, 15:0, i-15:0, and 17:1 was generally higher, and increased from 15.4% of total fatty acids in early exponential growth phase to 33.2% in the stationary phase. Reduction of the dilution rate in a chemostat from 0.27 to 0.065 h–1 also led to an almost threefold increase in the proportion of odd-numbered residues at the expense of the even-numbered normal ones. Contrary to this plasticity in the overall fatty acid profile influenced by variations in nutrient composition and availability, the level of eicosapentaenoic acid seemed exclusively dictated by growth temperature. The synthesis of this polyunsaturated fatty acid may be a key regulatory process in maintaining membrane fluidity.

Polar front associated variation in prokaryotic community structure in Arctic shelf seafloor

Spatial variations in composition of marine microbial communities and its causes have largely been disclosed in studies comprising rather large environmental and spatial differences. In the present study, we explored if a moderate but temporally permanent climatic division within a contiguous arctic shelf seafloor was traceable in the diversity patterns of its bacterial and archaeal communities. Soft bottom sediment samples were collected at 10 geographical locations, spanning spatial distances of up to 640 km, transecting the oceanic polar front in the Barents Sea. The northern sampling sites were generally colder, less saline, shallower, and showed higher concentrations of freshly sedimented phytopigments compared to the southern study locations. Sampling sites depicted low variation in relative abundances of taxa at class level, with persistent numerical dominance by lineages of Gamma- and Deltaproteobacteria (57–66% of bacterial sequence reads). The Archaea, which constituted 0.7–1.8% of 16S rRNA gene copy numbers in the sediment, were overwhelmingly (85.8%) affiliated with the Thaumarchaeota. Beta-diversity analyses showed the environmental variations throughout the sampling range to have a stronger impact on the structuring of both the bacterial and archaeal communities than spatial effects. While bacterial communities were significantly influenced by the combined effect of several weakly selective environmental differences, including temperature, archaeal communities appeared to be more uniquely structured by the level of freshly sedimented phytopigments.

Microbial trimethylamine-N-oxide as a disease marker: something fishy?

ABSTRACT Production of trimethylamine-N-oxide (TMAO) via the gut microbiota has recently been proposed as an important pathophysiological mechanism linking ingestion of ‘unhealthy foods’, such as beef (containing carnitine) and eggs (containing choline), and the development of atherosclerosis. Hence, TMAO has gained attention as a novel biomarker for cardiovascular disease. However, fish and seafood contain considerable amounts of TMAO and are generally accepted as cardioprotective: a puzzling paradox that seems to have been neglected. We suspect that the TMAO story may be a red herring.

Biological surface-active compounds from marine bacteria

ABSTRACT Surface-active compounds (SACs) are widely used in different industries as well as in many daily consumption products. However, with the increasing concern for their environmental acceptability, attention has turned towards biological SACs which are biodegradable, less toxic and more environmentally friendly. In this work, 176 marine hydrocarbon-degrading bacterial isolates from petroleum-contaminated sites along the Norwegian coastline were isolated and screened for their capacity to produce biological SACs. Among them, 18 isolates were capable of reducing the surface tension of the culture medium by at least 20 mN m−1 and/or capable of maintaining more than 40% of the emulsion volume after 24 h when growing on glucose or kerosene as carbon and energy source. These isolates were members of the genera Pseudomonas, Pseudoalteromonas, Rhodococcus, Catenovulum, Cobetia, Glaciecola, Serratia, Marinomonas and Psychromonas. Two isolates, Rhodococcus sp. LF-13 and Rhodococcus sp. LF-22, reduced surface tension of culture medium by more than 40 mN m−1 when growing on kerosene, n-hexadecane or rapeseed oil. The biosurfactants were produced by resting cells of the two Rhodococcus strains suggesting the biosynthesis of the biosurfactants was not necessarily associated with their growth on hydrocarbons.

Perturbation of seafloor bacterial community structure by drilling waste discharge

Offshore drilling operations result in the generation of drill cuttings and localized smothering of the benthic habitats. This study explores bacterial community changes in the in the upper layers of the seafloor resulting from an exploratory drilling operation at 1400m water depth on the Barents Sea continental slope. Significant restructurings of the sediment microbiota were restricted to the sampling sites notably affected by the drilling waste discharge, i.e. at 30m and 50m distances from the drilling location, and to the upper 2cm of the seafloor. Three bacterial groups, the orders Clostridiales and Desulfuromonadales and the class Mollicutes, were almost exclusively confined to the upper two centimeters at 30m distance, thereby corroborating an observed increase in anaerobicity inflicted by the drilling waste deposition. The potential of these phylogenetic groups as microbial bioindicators of the spatial extent and persistence of drilling waste discharge should be further explored.