Community Structure of Nitrifying and Denitrifying Bacteria from Effluents Discharged into Lake Victoria, Kenya

An active microbial community of nitrifying and denitrifying bacteria is needed for efficient utilization of nitrogenous compounds from wastewater. In this study, we explored the bacterial community diversity and structure within rivers, treated and untreated wastewater treatment plants (WWTPs) discharging into Lake Victoria. Water samples were collected from rivers and WWTPs that drain into Lake Victoria. Physicochemical analysis was done to determine the level of nutrients or pollutant loading in the samples. Total community DNA was extracted, followed by Illumina high throughput sequencing to determine the total microbial community and abundance. Enrichment and isolation were then done to recover potential nitrifiers and denitrifiers. Physicochemical analysis pointed to high levels total nitrogen and ammonia in both treated and untreated WWTPs as compared to the samples from the lake and rivers. A total of 1,763 operational taxonomic units (OTUs) spread across 26 bacterial phyla were observed with the most dominant phylum being Proteobacteria. We observed a decreasing trend in diversity from the lake, rivers to WWTPs. The genus Planktothrix constituted 19% of the sequence reads in sample J2 collected from the lagoon. All the isolates recovered in this study were affiliated to three genera: Pseudomonas, Klebsiella and Enterobacter in the phylum Proteobacteria. A combination of metagenomic analysis and a culture-dependent approach helped us understand the relative abundance as well as potential nitrifiers and denitrifiers present in different samples. The recovered isolates could be used for in situ removal of nitrogenous compounds from contaminated wastewater.

Micrococcus luteus strain CGK112 isolated from cow dung demonstrated efficient biofilm-forming ability and degradation potential toward high-density polyethylene (HDPE)

Biodegradation is the most promising environmentally sustainable method that offers a significant opportunity with minimal negative environmental consequences while searching for solutions to this global problem of plastic pollution that has now spread to almost everywhere in the entire world. In the present work, HDPE-degrading bacterial strain CGK112 was isolated from the fecal matter of a cow. The bacterial strain was identified as Micrococcus luteus CGK112 by 16S rRNA sequence coding analysis. Significant weight loss, i.e., 3.85% was recorded in the HDPE film treated with strain CGK112 for 90 days. The surface micromorphology was examined using FE-SEM, which revealed spectacular bacterial colonization as well as structural deformation. Furthermore, the EDX study indicated a significant decrease in the atomic percentage of carbon content, whereas FTIR analysis confirmed functional groups alternation as well as an increase in the carbonyl index which can be attributed to the metabolic activity of biofilm. Our findings provide insight into the capacity of our strain CGK112 to colonize and utilize HDPE as a single carbon source, thus promoting its degradation.

Dynamic succession patterns and interactions of phyllospheric microorganisms during NOx exposure

The phyllosphere plays a role in alleviating air pollution, potentially leveraging the native microorganisms for further enhancement. It remains unclear how phyllospheric microorganisms respond to nitrogen oxide (NO_x) pollution and participate in abatement. Here, we exposed Schefflera octophylla to NO_x to reveal microbial succession patterns and interactions in the phyllosphere. During exposure, phyllospheric ammonium (NH₄⁺-N) significantly increased, with different alpha diversity changes between bacteria and fungi. Community successions enclosed core taxa with relatively excellent tolerance, represented by bacterial genera (Norcardiodes, Aeromicrobium) and fungal genera (Talaromyces, Acremonium). The exposure eliminated specific pathogens (e.g., Zymoseptoria) and benefitted plant growth-promoting populations (e.g., Talaromyces, Exiguobacterium), which might favor plant disease control, improve plant health and thus buffer NO_x pollution. Cooccurrence networks revealed more negative correlations among bacteria and closer linkages among fungi during exposure. Our results also showed a functional shift from the predominance of pathotrophs to saprotrophs. Our study identified microbial successions and interactions during NO_x pollution and thus enlightened prospective taxa and potential roles of phyllospheric microorganisms in NO_x remediation.

Spirosoma rhododendri sp. nov., isolated from a flower of royal azalea (Rhododendron schlippenbachii)

A Gram-negative, non-motile, strictly aerobic and rod- or filamentous-shaped strain, CJU-R4T, was isolated from a flower of royal azalea (Rhododendron schlippenbachii) collected in the Republic of Korea. Strain CJU-R4T was catalase-positive and oxidase-negative, and grew at 15–33 °C (optimum, 28–20 °C), at pH 5.0–8.0 (optimum, pH 7.0–8.0), and in the presence of 0–1 % NaCl (w/v; optimum, 0 %). Strain CJU-R4T had the highest 16S rRNA gene sequence similarity to Spirosoma oryzae RHs22T (96.6 %), revealing less than 93 % sequence similarity to other type strains. Phylogenetic and phylogenomic analysis also revealed strain CJU-R4T formed a robust cluster with S. oryzae RHs22T. The major fatty acids were summed feature 3 (comprising C16 : 1  ω7c and/or C16 : 1  ω6c; 33.0 %), C16 : 1  ω5c (22.1 %), iso-C15 : 0 (12.6 %) and C16 : 0 (10.7 %). The polar lipids were composed of phosphatidylethanolamine, three unidentified aminophospholipids, one unidentified phospholipid and four unidentified lipids. Menaquinone-7 was detected as the sole respiratory quinone. The genomic DNA G+C content was 55.2 mol%. The average nucleotide identity and digital DNA–DNA hybridization values between strain CJU-R4T and Spirosoma oryzae DSM 28354T were 81.5 and 23.9 %, respectively. Based on the results of the phenotypic and genotypic analyses, strain CJU-R4T is considered to represent a novel species of the genus Spirosoma , for which the name Spirosoma rhododendri sp. nov. is proposed. The type strain is CJU-R4T (=KACC 21264T=NBRC 114513T).

Kangiella shandongensis sp. nov., a novel species isolated from saltern in Yantai, China

A Gram-stain-negative, wheat, rod-shaped, non-motile, non-spore forming, and facultatively anaerobic bacterium strain, designated as PI^T, was isolated from saline silt samples collected in saltern in Yantai, Shandong, China. Growth was observed within the ranges 4-45 °C (optimally at 33 °C), pH 6.0-9.0 (optimally at pH 7.0) and 1.0-11.0% NaCl (optimally at 3.0%, w/v). Strain PI^T showed highest 16S rRNA gene sequence similarity to Kangiella sediminilitoris BB-Mw22^T (98.3%) and Kangiella taiwanensis KT1^T (98.3%). The major cellular fatty acids (> 10% of the total fatty acids) were iso-C_15:0 (52.7%) and summed featured 9 (iso-C_17:1ω9c/C_16:0 10-methyl, 11.8%). The major polar lipids identified were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylmonomethylethanolamine and phosphatidylglycerol. The major respiratory isoprenoid quinone was Q-8. The G + C content of the genomic DNA was 45.8%. Average Nucleotide Identity values between whole genome sequences of strain PI^T and next related type strains supported the novel species status. Based on physiological, biochemical, chemotaxonomic characteristics and genomic analysis, strain PI^T is considered to represent a novel species within the genus Kangiella, for which the name Kangiella shandongensis sp. nov. is proposed. The type strain is PI^T (= KCTC 82509 ^T = MCCC 1K04352^T).

Spirosoma profusum sp. nov., and Spirosoma validum sp. nov., radiation-resistant bacteria isolated from soil in South Korea

Two novel Gram-negative, rod-shaped bacterial strains BT702^T and BT704^T were isolated from soil collected in Jeongseon (37° 22' 45″ N, 128° 39' 53″ E), Gangwon province, South Korea. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strains BT702^T and BT704^T belong to distinct lineage within the genus Spirosoma (family Cytophagaceae, order Cytophagales, class Cytophagia and phylum Bacteroidetes). The strain BT702^T was closely related to Spirosoma flavus 15J11-2^T (96.7% 16S rRNA gene similarity) and Spirosoma metallilatum TX0405^T (93.3%). The strain BT704^T was closely related to Spirosoma koreense 15J8-5^T (94.6%), Spirosoma endophyticum DSM 26130^T (93.8%) and Spirosoma humi S7-4-1^T (93.8%). The genome sizes of type strains BT702^T and BT704^T are 8,731,341 bp and 8,221,062 bp, respectively. The major cellular fatty acids of strains BT702^T and BT704^T were C_16:1 ω5c and summed feature 3 (C_16:1 ω6c/C_16:1 ω7c). The strains were found to have the same quinone system, with MK-7 as the major respiratory quinone. The major polar lipids of strain BT702^T was identified to be phosphatidylethanolamine (PE), aminophospholipid (APL) and aminolipid (AL), while that of strain BT704^T consisted of phosphatidylethanolamine (PE) and aminophospholipid (APL). Based on the polyphasic analysis (phylogenetic, chemotaxonomic and biochemical), strains BT702^T and BT704^T can be suggested as two new bacterial species within the genus Spirosoma and the proposed names are Spirosoma profusum and Spirosoma validum, respectively. The type strain of Spirosoma profusum is BT702^T (= KCTC 82115^T = NBRC 114859^T) and type strain of Spirosoma validum is BT704^T (= KCTC 82114^T = NBRC 114966^T).

Spirosoma utsteinense sp. nov. isolated from Antarctic ice-free soils from the Utsteinen region, East Antarctica

Between 2014 and 2016, 16 Gram-stain-negative, aerobic, rod-shaped and yellow-orange pigmented bacteria were isolated from exposed soils from the Utsteinen region, Sør Rondane Mountains, East Antarctica. Analysis of their 16S rRNA gene sequences revealed that the strains form a separate cluster in the genus Spirosoma, with Spirosoma rigui KCTC 12531^T as its closest neighbour (97.8 % sequence similarity). Comparative genome analysis of two representative strains (i.e. R-68523^T and R-68079) of the new group with the type strains of Spirosoma rigui (its closest neighbour) and Spirosoma linguale (type species of the genus), yielded average nucleotide identity values of 73.9-78.7 %. Digital DNA-DNA reassociation values of the two strains and these type strains ranged from 20.3 to 22.0 %. The predominant cellular fatty acids of the two novel strains were summed feature 3 (i.e. C_16 : 1  ω7c and/or iso-C₁₅ 2-OH), C_16 : 1  ω5c, C_16 : 0 and iso-C_15 : 0. The new Spirosoma strains grew with 0-0.5 % (w/v) NaCl, at pH 6.5-8.0 and displayed optimum growth between 15 and 25 °C. Based on the results of phenotypic, genomic, phylogenetic and chemotaxonomic analyses, the new strains represent a novel species of the genus Spirosoma for which the name Spirosoma utsteinense sp. nov. is proposed. The type strain is R-68523^T (=LMG 31447^T=CECT 9925^T).

Spirosoma telluris sp. nov. and Spirosoma arboris sp. nov. isolated from soil and tree bark, respectively

Two novel strains (HMF3257T and HMF4905T), isolated from freshwater and bark samples, were investigated to determine their relationships within and between species of the genus Spirosoma by using a polyphasic approach. They were aerobic, Gram-stain-negative, non-motile and rod-shaped bacteria. The major fatty acids (>10%) in both strains were identified as summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c) and C16 : 1 ω5c, while strains HMF3257T and HMF4905T contained a moderately high amount of C16 : 0 and iso-C15 : 0, respectively. The predominant respiratory quinone was MK-7 for both strains. In addition to phosphatidylethanolamine and one unidentified glycolipid, the polar lipid profile of strain HMF3257T consisted of three unidentified aminophospholipids, one unidentified aminolipid and two unidentified polar lipids, and that of strain HMF4905T consisted of one unidentified aminophospholipid, two unidentified aminolipids and three unidentified polar lipids. The DNA G+C contents of strains HMF3257T and HMF4905T were 47.2 and 46.4 mol%, respectively. Phylogenetic analysis based on 16S rRNA gene sequences showed that strains HMF3257T and HMF4905T are closely related to Spirosoma migulaei 15J9-8T (97.0 % sequence similarity), while sharing 97.4 % sequence similarity with each other. The average nucleotide identity value between strains HMF3257T and HMF4905T was 81.1 %, and the digital DNA–DNA hybridization value between these two strains was 24.4 %. Based on the above data, strains HMF3257T and HMF4905T represent two novel members within the genus Spirosoma , for which the names Spirosoma telluris sp. nov. and Spirosoma arboris sp. nov. are proposed, respectively. The type strain of S. telluris is HMF3257T (=KCTC 62463T=NBRC 112670T) and type strain of S. arboris is HMF4905T (=KCTC 72779T=NBRC 114270T).