Roseicyclus amphidinii sp. nov., a novel bacterium isolated from the culture of a dinoflagellate Amphidinium carterae

A Gram-negative, rod-shaped and light pink-pigmented bacterial strain, designated Amp-Y-6T, was isolated from the culture of a dinoflagellate Amphidinium carterae CCMP1314. It can produce bacteriochlorophyll a. The 16S rRNA gene of strain Amp-Y-6T had the highest sequence similarity with Roseicyclus marinus CCMM001T of 98.1%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain Amp-Y-6T was affiliated to the genus Roseicyclus and formed a monophyletic clade with R. marinus CCMM001T and Roseicyclus mahoneyensis ML6T. The digital DNA-DNA hybridization, average nucleotide identity and average amino acid identity between strain Amp-Y-6T and the two phylogenetic relatives were 22.7-22.8, 80.4-80.5 and 79.5-80.2%, respectively. The respiratory quinone was Q-10. The major fatty acid composition was summed feature 8 (C18:1  ω7c and/or C18:1  ω6c). The draft genome size was 3.8 Mbp with a genomic G+C content of 68.1 mol%. Gene annotation showed that Amp-Y-6T contained a gene cluster responsible for the C-P degradation, indicating that it had the potential to provide a phosphate source for the dinoflagellate. Based on the phylogenetic, phenotypic and chemotaxonomic characteristics, strain Amp-Y-6T represents a novel species, for which the name Roseicyclus amphidinii sp. nov. is proposed. The type strain is Amp-Y-6T (=MCCC 1K08249T=KCTC 92882T).

Roseicyclus sediminis sp. nov. and Roseicyclus salinarum sp. nov., isolated from marine environment, and reclassification of two species of the genus Roseibacterium as species of the genus Roseicyclus

Two Gram-stain-negative, facultatively anaerobic, rod-shaped bacteria were isolated from coastal sediments and salt marshes in Weihai, China, and designated as SDUM158017T and SDUM158016T, respectively. Both grew at temperatures ranging from 20 to 43°C and within a pH range of 6.0 to 9.0. However, strain SDUM158016T grew in the presence of 1.0-7.0% (w/v) NaCl, whereas strain SDUM158017T was able to grow in the presence of 1.0-10.0% (w/v) NaCl. Strains SDUM158016T and SDUM158017T contain major fatty acids of C18 : 1 ω7ϲ and C16 : 0 and contain Q10 as the sole quinone. Based on 16S rRNA gene sequence analysis, the closest relatives of strains SDUM158016T and SDUM158017T are 'Roseibacterium beibuensis' MCCC 1F00103T, followed by Roseibacterium elongatum JCM 11220T, with the highest similarities 97.1 and 97.3 %, respectively. The average nucleotide identity values between strain SDUM158016T and species of the genera Roseibacterium and Roseicyclus ranged from 76.0 to 78.9 %, while they ranged from 75.9 to 78.6% for strain SDUM158017T. These values are below the species delineation threshold of 98.6%, suggesting that both strains represent novel species. Phylogenetic analysis of the 16S rRNA genes and genome sequences further indicates that Roseibacterium species within the genus Roseicyclus and these isolates represent two potentially novel species within the genus Roseicyclus. Taken together, strains SDUM158017T and SDUM158016T represent two novel species of the genus Roseicyclus, for which the names Roseicyclus sediminis and Roseicyclus salinarum are proposed with the type strains SDUM158016T (=KCTC 92632T =MCCC 1H01367T) and SDUM158017T (=KCTC 92633T =MCCC 1H01363T), respectively. Based on phylogenetic and genomic analyses, we also propose the reclassification of Roseibacterium elongatum as Roseicyclus elongatus comb. nov. and Roseibacterium persicicum as Roseicyclus persicicus comb. nov.

Long-Term Survival of Synechococcus and Heterotrophic Bacteria without External Nutrient Supply after Changes in Their Relationship from Antagonism to Mutualism

Marine phytoplankton and heterotrophic bacteria share a very close but usually changeable relationship. However, the ultimate fate of their unstable relationship on a long-term scale is unclear. Here, the relationship between Synechococcus and heterotrophic bacterial communities underwent a dramatic shift from antagonism to commensalism and eventually to mutualism during long-term cocultivation. The relationship change is attributed to the different (even opposite) effects of diverse bacterial members on Synechococcus and the ratio of beneficial to harmful bacteria. Different bacterial members also interact with each other (e.g., quorum-sensing communication, hostility, or mutual promotion) and drive a dynamic succession in the entire community structure that corresponds exactly to the shift in its relationship with Synechococcus. In the final mutualism stage, a self-sufficient nitrogen cycle, including nitrogen fixation, denitrification, and organic nitrogen degradation, contributed to the healthy survival of Synechococcus for 2 years without an exogenous nutrient supply. This natural selective trait of Synechococcus and heterotrophic bacteria toward mutualism under long-term coexistence provides a novel clue for understanding the ubiquity and competitive advantage of Synechococcus in global oceans.

Pseudoroseicyclus tamaricis sp. nov., isolated from seashore sediment of a Tamarix chinensis forest and emended descriptions of the genus Pseudoroseicyclus Park et al. 2016

An aerobic, Gram-stain-negative, bacterium, designated CLL3-39^T was isolated from seashore sediment collected at a Tamarix chinensis forest in the Marine Ecology Special Reserve of Changyi, Shandong Province, PR China. Cells of strain CLL3-39^T were olive-shaped and no flagellum was observed. Strain CLL3-39^T grew optimally at 33 °C, pH 7.5 and salinity (sea salts) of 40 g l^-1. The main fatty acids in the cell membrane of strain CLL3-39^T comprised anteiso-C_15 : 0 (22.3 %), iso-C_15 : 0 (14.0 %), C_16 : 0 (9.2 %) and summed feature 8 (contains C_18 : 1  ω7c/C_18 : 1  ω6c. 26. 7 %). The main polar lipids of CLL3-39^T were phosphatidylglycerol, diphosphatidylglycerol and phosphatidylcholine. The respiratory quinone was Q10. The G+C content of the genomic DNA of strain CLL3-39^T was 69.6 mol%. The average nucleotide identity between CLL3-39^T and Pseudoroseicyclus aestuarii DB-4^T was 74.7 % and the in silico DNA-DNA hybridization value was 20.1 %. Phylogenetically, strain CLL3-39^T belonged to the genus Pseudoroseicyclus, branching with only one type strain P. aestuarii DB-4^T with 96.3 % 16S rRNA gene similarity, followed by Limimaricola cinnabarinus LL-001^T (95.2 %). Based on its phenotypic, phylogenetic and chemotaxonomic characteristics, we propose strain CLL3-39^T (=MCCC 1A14815^T =KCTC 72665^T) as a representative of a novel species in the genus Pseudoroseicyclus, for which the name Pseudoroseicyclus tamaricis sp. nov. is proposed.

Influence of photobioreactor set-up on the survival of microalgae inoculum

Cultivation of specific microalgae is still difficult in an industrial setup as contamination and balancing the economic cost are not always possible. Understanding the ecology of cultivation of microalgae is therefore necessary to implement stable production. The aim of the study was to understand how different types of photobioreactors and types of culture medium influenced the survival of a specific microalgae inoculum, S. almeriensis. The bacterial and microalgae community were studied using Illumina sequencing. Only the closed configuration was able to maintain the inoculated species while all the other systems developed a different eukaryotic community due to contamination and the higher fitness of contaminants. Photobioreactor configuration was more important than medium in shaping the eukaryotes community, while the bacterial community was influenced strongly by both. Results showed that even a well-adapted strain is maintained only in the closed reactor while the open reactors are colonized by a multispecies consortium.