Prosthecate aerobic anoxygenic phototrophs Photocaulis sulfatitolerans gen. nov. sp. nov. and Photocaulis rubescens sp. nov. isolated from alpine meromictic lakes in British Columbia, Canada.

Seven Gram-negative flagellated and subsequent prosthecate bacteria were isolated from meromictic Mahoney Lake and Blue Lake in British Columbia, Canada. Each became pink-red after 1-2 weeks of incubation, containing bacteriochlorophyll a incorporated into light harvesting and reaction center pigment-protein complexes. They did not grow anaerobically under illuminated conditions, supporting their identification as obligate aerobic anoxygenic phototrophs (AAP). All isolates preferred high salinity and BL14T tolerated up to 6.5% NaCl or 16.0% Na2SO4. In addition to phenotypic differences, analysis of 16S rRNA gene sequences found both strains BL14T and ML37T were related to Alkalicaulis satelles, G-192T by 98.41 and 98.84%, respectively, and distantly associated to members of the non-phototrophic genus Glycocaulis profundi, ZYF765T (95.59 and 95.36%, respectively) within the newly recognized Maricaulales order of α-Proteobacteria. BL14T and ML37T contained photosynthetic operons of 46,143 and 46,315 bp, where genes of BL14T were uniquely split into two distal operons. Furthermore, A. satelles was not originally published as an AAP, but was also found in this work to contain a similar 45,131 bp fragment. The distinct morphological features, physiological traits and genomic analysis including average nucleotide identity and digital DNA:DNA hybridization of circularized genomes supported the proposal of new genus and species Photocaulis sulfatitolerans gen. nov. sp. nov., type strain BL14T and Photocaulis rubescens sp. nov. type strain ML37T.

Soil Bacterial Diversity Is Positively Correlated with Decomposition Rates during Early Phases of Maize Litter Decomposition.

This study aimed to investigate the effects of different levels of soil- and plant-associated bacterial diversity on the rates of litter decomposition, and bacterial community dynamics during its early phases. We performed an incubation experiment where soil bacterial diversity (but not abundance) was manipulated by autoclaving and reinoculation. Natural or autoclaved maize leaves were applied to the soils and incubated for 6 weeks. Bacterial diversity was assessed before and during litter decomposition using 16S rRNA gene metabarcoding. We found a positive correlation between litter decomposition rates and soil bacterial diversity. The soil with the highest bacterial diversity was dominated by oligotrophic bacteria including Acidobacteria, Nitrospiraceae, and Gaiellaceae, and its community composition did not change during the incubation. In the less diverse soils, those taxa were absent but were replaced by copiotrophic bacteria, such as Caulobacteraceae and Beijerinckiaceae, until the end of the incubation period. SourceTracker analysis revealed that litter-associated bacteria, such as Beijerinckiaceae, only became part of the bacterial communities in the less diverse soils. This suggests a pivotal role of oligotrophic bacteria during the early phases of litter decomposition and the predominance of copiotrophic bacteria at low diversity.

Brevundimonas humi sp. nov., an alphaproteobacterium isolated from forest soil.

During a study of bacterial diversity of soil, a novel strain, CA-15T, was isolated from Kyonggi University forest soil. Cells were aerobic, Gram-stain-negative, motile, non-spore-forming, rod-shaped, oxidase-positive and catalase- negative. Tyrosine was not oxidized but produced red pigmentation on an agar palte. Strain CA-15T hydrolysed Tween 60 and DNA. It grew at 15-35 °C (optimum, 25-30 °C), pH 6.0-10.0 (optimum, 7.0-9.0) and at 1.5 % (w/v) NaCl concentration. Phylogenetic analysis based on its 16S rRNA gene sequence indicated that strain CA-15T formed a lineage within the family Caulobacteraceae of the class Alphaproteobacteria that was distinct from various species of the genus Brevundimonas. Brevundimonas bullata DSM 7126T was the closest member of strain CA-15T on the basis of 16S rRNA gene sequence similarity (98.48 %). Q-10 was only an isoprenoid quinone detected for strain CA-15T. The major polar lipids were 1,2-di-O-acyl-3-O-[d-glucopyranosyl-(1→4)-αd-glucopyranuronosyl]glycerol, 1,2-di-O-acyl-3-O-[αd-glucopyranosyl]-sn-glycerol, 1,2-di-O-acyl-3-O-αd-glucopyranuronosylglycerol, 1,2-diacyl-3-O-[6'-phosphatidyl-αd-glucopyranosyl]glycerol and phosphatidylglycerol. The major cellular fatty acids were summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c), C16 : 0, C18 : 1ω7c 11-methyl and C17 : 1ω8c. The DNA G+C content of strain CA-15T was 63.6 mol%. The polyphasic characterization indicated that strain CA-15T represents a novel species in the genus Brevundimonas, for which the name Brevundimonas humi sp. nov. is proposed. The type strain of Brevundimonas humi is CA-15T (=KEMB 9005-528T=KACC 19106T=NBRC 112677T).