Additions to the genus Gimesia: description of Gimesia alba sp. nov., Gimesia algae sp. nov., Gimesia aquarii sp. nov., Gimesia aquatilis sp. nov., Gimesia fumaroli sp. nov. and Gimesia panareensis sp. nov., isolated from aquatic habitats of the Northern Hemisphere

Thirteen novel planctomycetal strains were isolated from five different aquatic sampling locations. These comprise the hydrothermal vent system close to Panarea Island (Italy), a biofilm on the surface of kelp at Monterey Bay (CA, USA), sediment and algae on Mallorca Island (Spain) and Helgoland Island (Germany), as well as a seawater aquarium in Braunschweig, Germany. All strains were shown to belong to the genus Gimesia. Their genomes cover a size range from 7.22 to 8.29 Mb and have a G+C content between 45.1 and 53.7%. All strains are mesophilic (Topt 26-33 °C) with generation times between 12 and 32 h. Analysis of fatty acids yielded palmitic acid (16:0) and a fatty acid with the equivalent chain length of 15.817 as major compounds. While five of the novel strains belong to the already described species Gimesia maris and Gimesia chilikensis, the other strains belong to novel species, for which we propose the names Gimesia alba (type strain Pan241wT = DSM 100744T = LMG 31345T = CECT 9841T = VKM B-3430T), Gimesia algae (type strain Pan161T = CECT 30192T = STH00943T = LMG 29130T), Gimesia aquarii (type strain V144T = DSM 101710T = VKM B-3433T), Gimesia fumaroli (type strain Enr17T = DSM 100710T = VKM B-3429T) and Gimesia panareensis (type strain Enr10T = DSM 100416T = LMG 29082T). STH numbers refer to the Jena Microbial Resource Collection (JMRC).

Comparison of the compatible solute pool of two slightly halophilic planctomycetes species, Gimesia maris and Rubinisphaera brasiliensis

Gimesia maris and Rubinisphaera brasiliensis are slightly halophilic representatives of the deep-branching phylum Planctomycetes. For osmoadaptation both species accumulated α-glutamate, sucrose, ectoine and hydroxyectoine. A major role was found for ectoine, hydroxyectoine as well as sucrose under hyper-osmotic shock conditions. Nevertheless, the levels of sucrose were up-regulated by the increased salinity levels and also by low nitrogen availability. Additionally, G. maris accumulated glucosylglycerate (GG) as major solute specifically under low nitrogen levels, which prompted us to analyse the transcript abundance of two homologues genes known for the biosynthesis of GG, namely glucosyl-3-phosphoglycerate synthase (GpgS) and glucosyl-3-phosphoglycerate phosphatase (GpgP). By qPCR using a suitable reference gene selected in this study, the transcript abundance of the biosynthetic genes was quantified in G. maris cells under hyper-osmotic shock or under low nitrogen conditions. The gpgS gene was induced under nitrogen-limiting conditions suggesting that GG synthesis is regulated primarily at the transcription level. Moreover, the expression of a gene coding for a putative sucrose-phosphorylase (Spase) located upstream the gpgS and gpgP genes was up-regulated, predicting a metabolic role of Spase probably related to GG synthesis.

Development of Genetic Tools for the Manipulation of the Planctomycetes

Bacteria belonging to the Planctomycetes, Verrucomicrobia, Chlamydiae (PVC) superphylum are of interest for biotechnology, evolutionary cell biology, ecology, and human health. Some PVC species lack a number of typical bacterial features while others possess characteristics that are usually more associated to eukaryotes or archaea. For example, the Planctomycetes phylum is atypical for the absence of the FtsZ protein and for the presence of a developed endomembrane system. Studies of the cellular and molecular biology of these infrequent characteristics are currently limited due to the lack of genetic tools for most of the species. So far, genetic manipulation in Planctomycetes has been described in Planctopirus limnophila only. Here, we show a simple approach that allows mutagenesis by homologous recombination in three different planctomycetes species (i.e., Gemmata obscuriglobus, Gimesia maris, and Blastopirellula marina), in addition to P. limnophila, thus extending the repertoire of genetically modifiable organisms in this superphylum. Although the Planctomycetes show high resistance to most antibiotics, we have used kanamycin resistance genes in G. obscuriglobus, P. limnophila, and G. maris, and tetracycline resistance genes in B. marina, as markers for mutant selection. In all cases, plasmids were introduced in the strains by mating or electroporation, and the genetic modification was verified by Southern Blotting analysis. In addition, we show that the green fluorescent protein (gfp) is expressed in all four backgrounds from an Escherichia coli promoter. The genetic manipulation achievement in four phylogenetically diverse planctomycetes will enable molecular studies in these strains, and opens the door to developing genetic approaches not only in other planctomycetes but also other species of the superphylum, such as the Lentisphaerae.