A polyphasic taxonomic study was performed to characterize dissimilatory iron-reducing strains mostly isolated from Antarctic sea ice. The strains were isolated from samples of congelated (land-fast) sea ice, grease ice, and ice algal biomass collected from the coastal areas of the Vestfold Hills in eastern Antarctica (68°S 78°E). The strains were facultatively anaerobic, motile, and rod shaped, were capable of anaerobic growth either by fermentation of carbohydrates or by anaerobic respiration, and utilized a variety of electron acceptors, including nitrate, ferric compounds, and trimethylamine N-oxide. A phylogenetic analysis performed with 16S rRNA sequences showed that the isolates formed two groups representing novel lineages in the genus Shewanella. The first novel group included seawater-requiring, psychrophilic, chitinolytic strains which had DNA G+C contents of 48 mol%. The members of the second strain group were psychrotrophic and did not require seawater but could tolerate up to 9% NaCl. The strains of this group were also unable to degrade polysaccharides but could utilize a number of monosaccharides and disaccharides and had G+C contents of 40 to 43 mol%. The whole-cell-derived fatty acid profiles of the sea ice isolates were found to be similar to the profiles obtained for other Shewanella species. The omega-3 polyunsaturated fatty acid eicosapentaenoic acid (EPA) (20:5ω3) was detected in all of the sea ice isolates at levels ranging from 2 to 16% of the total fatty acids. EPA was also found at high levels in Shewanella hanedai (19 to 22%) and Shewanella benthica (16 to 18%) but was absent in Shewanella alga and Shewanella putrefaciens. On the basis of polyphasic taxonomic data, the Antarctic iron-reducing strains are placed in two new species, Shewanella frigidimarina sp. nov. (type strain, ACAM 591) and Shewanella gelidimarina sp. nov. (type strain, ACAM 456).

Several orange- and yellow-pigmented, halophilic, strictly aerobic, chemoheterotrophic, Gram-negative strains were isolated during investigations of maritime Antarctic habitats, including coastal fast sea-ice brine and algae, crustaceans and quartz stone sublithic cyanobacterial biofilms. Isolates investigated in this study belonged to the marine clade of the familyFlavobacteriaceaeand represented lineages that were either distinct from species with validly published names or appeared to be distinct species within existing genera. A polyphasic taxonomic analysis demonstrated the novelty of these strains, and several new taxa are proposed. Strains from quartz stone sublithic communities were grouped into two new genera designatedSubsaximicrobiumgen. nov. andSubsaxibactergen. nov. The genusSubsaximicrobiumincluded the speciesSubsaximicrobium wynnwilliamsiisp. nov. (type species; type strain G#7^T=ACAM 1070^T=CIP 108525^T) andSubsaximicrobium saxinquilinussp. nov. (type strain Y4-5^T=ACAM 1063^T=CIP 108526^T). The genusSubsaxibactercontained a single species designatedSubsaxibacter broadyisp. nov. (type strain P7^T=ACAM 1064^T=CIP 108527^T). A novel bacterial strain isolated from the lake-dwelling, calanoid copepodParalabidocera antarcticawas given the nameLacinutrix copepodicolagen. nov., sp. nov. (type strain DJ3^T=ACAM 1055^T=CIP 108538^T). Four novel species of the genusBizioniawere discovered,Bizionia algoritergicolasp. nov. (type strain APA-1^T=ACAM 1056^T=CIP 108533^T) andBizionia myxarmorumsp. nov. (type strain ADA-4^T=ACAM 1058^T=CIP 108535^T), which were isolated from the carapace surfaces of sea-ice algae-feeding amphipods, andBizionia gelidisalsuginissp. nov. (type strain IC164^T=ACAM 1057^T=CIP 108536^T) andBizionia saleffrenasp. nov. (type strain HFD^T=ACAM 1059^T=CIP 108534^T), which were isolated from sea-ice brines. Several other novel species were also isolated from sea-ice samples, including two novel species of the genusGelidibacter,Gelidibacter gilvussp. nov. (type strain IC158^T=ACAM 1054^T=CIP 108531^T) andGelidibacter salicanalissp. nov. (type strain IC162^T=ACAM 1053^T=CIP 108532^T), as well as three novel species of the genusGillisia,Gillisia illustriluteasp. nov. (type strain IC157^T=ACAM 1062^T=CIP 108530^T),Gillisia sandarakinasp. nov. (type strain IC148^T=ACAM 1060^T=CIP 108529^T) andGillisia hiemivividasp. nov. (type strain IC154^T=ACAM 1061^T=CIP 108528^T).

A group of sea-ice-derived psychrophilic bacterial strains possessing the unusual ability to synthesize the polyunsaturated fatty acids eicosapentaenoic acid (20:5.3) and arachidonic acid (20:4.6) belong to the Family Flavobacteriaceae (Flexibacter-Bacteroides-Flavobacterium phylum), according to 16S rRNA sequence analysis. Surprisingly, the isolates were also found to cluster closely to the moderately halophilic and psychrotrophic species [Flavobacterium] gondwanense (sequence similarity 97-8-98-1 %). The whole-cell fatty acid profiles of this group and [Flavobacterium] gondwanense were very similar and distinct from other related flavobacteria. The sea ice strains and [Flavobacterium] gondwanense differed substantially in terms of ecophysiology, possibly representing divergent adaptations to sympagic and planktonic marine habitats, respectively. Evidence based on phylogeny and fatty acid profiles supports the conclusion that the taxa are close relatives distinct from other bacterial groups. It is thus proposed that the sea ice strains represent a novel taxon designated Psychroflexus torquis gen. nov., sp., nov. (type strain ACAM 623^T) while [Flavobacterium] gondwanense becomes Psychroflexus gondwanense gen. nov., comb. nov.

Semidwarfing genes have improved crop yield by reducing height, improving lodging resistance, and allowing plants to allocate more assimilates to grain growth. In wheat (Triticum aestivum), the Rht18 semidwarfing gene was identified and deployed in durum wheat before it was transferred into bread wheat, where it was shown to have agronomic potential. Rht18, a dominant and gibberellin (GA) responsive mutant, is genetically and functionally distinct from the widely used GA-insensitive semidwarfing genes Rht-B1b and Rht-D1b. In this study, the Rht18 gene was identified by mutagenizing the semidwarf durum cultivar Icaro (Rht18) and generating mutants with a range of tall phenotypes. Isolating and sequencing chromosome 6A of these “overgrowth” mutants showed that they contained independent mutations in the coding region of GA2oxA9. GA2oxA9 is predicted to encode a GA 2-oxidase that metabolizes GA biosynthetic intermediates into inactive products, effectively reducing the amount of bioactive GA (GA₁). Functional analysis of the GA2oxA9 protein demonstrated that GA2oxA9 converts the intermediate GA₁₂ to the inactive metabolite GA₁₁₀. Furthermore, Rht18 showed higher expression of GA2oxA9 and lower GA content compared with its tall parent. These data indicate that the increased expression of GA2oxA9 in Rht18 results in a reduction of both bioactive GA content and plant height. This study describes a height-reducing mechanism that can generate new genetic diversity for semidwarfism in wheat by combining increased expression with mutations of specific amino acid residues in GA2oxA9.

Direct analysis of membrane lipids by liquid chromatography-electrospray mass spectrometry was used to demonstrate the role of unsaturation in ether lipids in the adaptation of Methanococcoides burtonii to low temperature. A proteomics approach using two-dimensional liquid chromatography-mass spectrometry was used to identify enzymes involved in lipid biosynthesis, and a pathway for lipid biosynthesis was reconstructed from the M. burtonii draft genome sequence. The major phospholipids were archaeol phosphatidylglycerol, archaeol phosphatidylinositol, hydroxyarchaeol phosphatidylglycerol, and hydroxyarchaeol phosphatidylinositol. All phospholipid classes contained a series of unsaturated analogues, with the degree of unsaturation dependent on phospholipid class. The proportion of unsaturated lipids from cells grown at 4°C was significantly higher than for cells grown at 23°C. 3-Hydroxy-3-methylglutaryl coenzyme A synthase, farnesyl diphosphate synthase, and geranylgeranyl diphosphate synthase were identified in the expressed proteome, and most genes involved in the mevalonate pathway and processes leading to the formation of phosphatidylinositol and phosphatidylglycerol were identified in the genome sequence. In addition, M. burtonii encodes CDP-inositol and CDP-glycerol transferases and a number of homologs of the plant geranylgeranyl reductase. It therefore appears that the unsaturation of lipids may be due to incomplete reduction of an archaeol precursor rather than to a desaturase mechanism. This study shows that cold adaptation in M. burtonii involves specific changes in membrane lipid unsaturation. It also demonstrates that global methods of analysis for lipids and proteomics linked to a draft genome sequence can be effectively combined to infer specific mechanisms of key biological processes.