Emticicia soli sp. nov., a novel member of the family 'Flexibacteraceae', isolated from tetrabromobisphenol A-contaminated soil

Emticicia fluvialis sp. nov., a potential hormone-degrading bacterium isolated from Nakdong River, Republic of Korea

A novel species of the genus Emticicia, designated BHSR1T, was isolated from a water sample that was collected from the Nakdong River, Republic of Korea, and its taxonomic affiliation was studied using a polyphasic approach. This bacterium was Gram-stain-negative, non-motile, aerobic, curved, rod-shaped, and oxidase- and catalase-negative. The bacterium grew optimally at 37 °C, pH 7.5 and 0% (w/v) NaCl. Phylogenetic analyses based on 16S rRNA gene sequences indicated that strain BHSR1T should be affiliated with the genus Emticicia, with a high similarity to Emticicia fontis KCTC 52248T (98.10%). Phylogenomic analysis also suggested that the strain represents a novel species in the genus Emticicia. The genomic G + C content was 41.9%. The average nucleotide identity, average amino acid identity and digital DNA-DNA hybridization between strain BHSR1T and its closely related relatives in the genus Emticicia were in ranges of 71.1-75.8%, 69.4-77.5% and 18.6-19.9%, respectively. The gene cluster within BHSR1T contained genes encoding enzymes that could be involved in hormone degradation. The major cellular fatty acids (> 10%) were summed feature 3 (comprising C16:1ω6c and/or C16:1ω7c) and iso-C15:0. With regards to the polar lipid profile, phosphatidylethanolamine (PE), two unidentified aminolipids and three unidentified lipids were identified as the major compounds. The major respiratory quinone was menaquinone (MK)-7. Based on its phylogenetic, phenotypic, chemotaxonomic, and genomic features, strain BHSR1T should be considered a novel species in the genus Emticicia of the family Spirosomaceae, for which the name Emticicia fluvialis sp. nov. is proposed. The type strain was considered BHSR1T (= KCTC 92622T = GDMCC 1.3740T).

Emticicia agri sp. nov., a novel member of the family Cytophagaceae

A bacterial strain, 17J42-9^T, was isolated from a soil sample collected on Jeju Island, Republic of Korea. Cells were observed to be Gram-stain negative and rod-shaped. Colonies were observed to be orange in colour on R2A agar. Analysis of 16S rRNA gene sequences showed that high levels of 16S rRNA sequence similarity were shared between 17J42-9^T and Emticicia fontis IMCC1731^T (98.2 %), Emticicia ginsengisoliGsoil 085^T (98.2 %) and Emticicia soli ZZ-4^T (97.8 %). Growth of strain 17J42-9^T was observed at 10-37 °C, pH 6.0-8.5 and in the presence of 0-0.5 % NaCl. The genomic G+C content was calculated to be 38.6 mol%. The predominant respiratory quinone of the isolate was found to be MK-7; the major fatty acids were identified as summed feature 3 (C_16 : 1 ω7c and/or C_16 : 1 ω6c) (34.1 %), C_15 : 0iso (23.4 %) and C_17 : 0iso 3-OH (10.8 %). The major polar lipids were found to be phosphatidylethanolamine, two unidentified aminolipids and an unidentified lipid. The phenotypic and chemotaxonomic data support the affiliation of strain 17J42-9^T with the genus Emticicia. However, the DNA-DNA relatedness between the isolate and its closest phylogenetic neighbours was lower than 46 %. The results of 16S rRNA gene sequence similarity analysis, DNA-DNA hybridization analysis and the observed differentiating phenotypic properties from other closely related taxa clearly indicate that strain 17J42-9^T represents a novel species in the genus Emticicia, for which the name Emticiciaagri sp. nov. is proposed. The type strain is 17J42-9^T (=KCTC 62270^T=JCM 33056^T).

Enhanced production of biomass and lipids by Euglena gracilis via co-culturing with a microalga growth-promoting bacterium, Emticicia sp. EG3

BACKGROUND

Euglena gracilis, a unicellular flagellated microalga, is regarded as one of the most promising species as microalgal feedstock for biofuels. Its lipids (mainly wax esters) are suitable for biodiesel and jet fuel. Culture of E. gracilis using wastewater effluent will improve the economics of E. gracilis biofuel production. Enhancement of the productivity of E. gracilis biomass is critical to creating a highly efficient biofuels production system. Certain bacteria have been found to promote microalgal growth by creating a favorable microenvironment. These bacteria have been characterized as microalgae growth-promoting bacteria (MGPB). Co-culture of microalgae with MGPB might offer an effective strategy to enhance microalgal biomass production in wastewater effluent culture systems. However, no MGPB has been identified to enhance the growth of E. gracilis. The objectives of this study were, therefore, to isolate and characterize the MGPB effective for E. gracilis and to demonstrate that the isolated MGPB indeed enhances the production of biomass and lipids by E. gracilis in wastewater effluent culture system.

RESULTS

A bacterium, Emticicia sp. EG3, which is capable of promoting the growth of microalga E. gracilis, was isolated from an E. gracilis-municipal wastewater effluent culture. Biomass production rate of E. gracilis was enhanced 3.5-fold and 3.1-fold by EG3 in the co-culture system using a medium of heat-sterilized and non-sterilized wastewater effluent, respectively, compared to growth in the same effluent culture but without EG3. Two-step culture system was examined as follows: E. gracilis was cultured with or without EG3 in wastewater effluent in the first step and was further grown in wastewater effluent in the second step. Production yields of biomass and lipids by E. gracilis were enhanced 3.2-fold and 2.9-fold, respectively, in the second step of the system in which E. gracilis was co-cultured with EG3 in the first step.

CONCLUSION

Emticicia sp. EG3 is the first MGPB for E. gracilis. Growth-promoting bacteria such as EG3 will be promising agents for enhancing E. gracilis biomass/biofuel productivities.