Sphingorhabdus buctiana sp. nov., isolated from fresh water, and reclassification of Sphingopyxis contaminans as Sphingorhabdus contaminans comb. nov

Sphingopyxis yananensis sp. nov., a novel 2-nitropropane degrading bacterium isolated from a microbial fermentation bed substrate

A rod-shaped, Gram-negative staining strain, FBM22^T, was isolated from a microbial fermentation bed substrate from a pig farm. Its colonies appeared yellow and were 0.5-1.2 mm in diameter. Cells were 0.3-0.5 μm wide, 0.5-0.83 μm long. Optimal growth occurred at 30 °C and pH 7.0-8.0; NaCl was not required for growth. The strain performed denitrification and nitrate reduction functions. And it could produce catalase. FBM22-1^T utilized the following organic substrates for growth: tyrosine, glutamic acid, D-glucose, and galactose. The novel isolate could degrade 2-nitropropane as carbon and nitrogen source. The dominant respiratory quinone was Q-10. The major polar lipids were diphosphatidylglycerol, phosphatidylcholine and phosphatidylethanolamine. C_18:1 ω7c, C_16:1 ω7c and/ or C_16:1 ω6c, and C_14:0 2-OH were the major (≥ 8%) fatty acids. The G+C content was 56.8 mol%. FBM22^T was found to be a member of the genus Sphingopyxis in the family Sphingomonadaceae of the class Alphaproteobacteria. It had the highest sequence similarity with the type strains Sphingopyxis terrae subsp. ummariensis UI2^T (96.47%) and Sphingopyxis terrae subsp. terrae NBRC 15098^T (96.40%). Furthermore, FBM22^T had 18.7% and 18.4% relatedness (based on digital DNA-DNA hybridization) with its two relatives (S. terrae subsp. ummariensis UI2^T and S. terrae subsp. terrae NBRC 15098^T). The morphological, physiological, and genotypic differences identified in this study support the classification of FBM22^T as a novel species within the genus Sphingopyxis, for which the name Sphingopyxis yananensis sp. nov. is proposed. The type strain is FBM22^T (= KCTC 82290^T = CCTC AB2020286^T).

Rhodococcus yananensis sp. nov., a novel denitrification actinobacterium isolated from microbial fermentation bed material from a pig farm

An opaque, pink-coloured, gram-positive, aerobic bacteria (designated as FBM22-1T), was isolated from microbial fermentation bed material from a pig farm in northwestern China. Optimal growth occurred at 30–37 °C, pH 7.0 and with 0.5 % NaCl (w/v). The strain had nitrification and denitrification functions. Phylogenetic analysis based on 16S rRNA gene sequences revealed that the novel isolate belonged to the genus Rhodococcus . Strain FBM22-1T was closely related to Rhodococcus zopfii NBRC 100606T and Rhodococcus rhodochrous NBRC 16069T, with 16S rRNA gene sequence similarities of 97.9 and 97.7 %, respectively. The predominant menaquinone in strain FBM22-1T was MK-8(H2). The cellular fatty acids consisted primarily of C16 : 1ω7c and/or C16 : 1 ω6c, C16 : 0 and 10-methyl C18 : 0. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine and glycolipid. The G+C content of strain FBM22-1T was 68.64 mol%. Based on the phenotypic, phylogenetic and chemotaxonomic characterization results, in combination with low values of digital DNA–DNA hybridization between strain FBM22-1T and its closest neighbours, FBM22-1T represents a novel species of the genus Rhodococcus , for which the name Rhodococcus yananensis sp. nov. is proposed; the type strain is FBM22-1T (=KCTC 49502T=CCTCC AB2020275T).

The genus Sphingopyxis: Systematics, ecology, and bioremediation potential - A review

The genus Sphingopyxis was first reported in the year 2001. Phylogenetically, Sphingopyxis is well delineated from other genera Sphingobium, Sphingomonas and Novosphingobium of sphingomonads group, family Sphingomonadaceae of Proteobacteria. To date (at the time of writing), the genus Sphingopyxis comprises of twenty validly published species available in List of Prokaryotic Names with Standing in Nomenclature. Sphingopyxis spp. have been isolated from diverse niches including, agricultural soil, marine and fresh water, caves, activated sludge, thermal spring, oil and pesticide contaminated soil, and heavy metal contaminated sites. Sphingopyxis species have drawn considerable attention not only for their ability to survive under extreme environments, but also for their potential to degrade number of xenobiotics and other environmental contaminants that impose serious threat to human health. At present, genome sequence of both cultivable and non-cultivable strains (metagenome assembled genome) are available in the public databases (NCBI) and genome wide studies confirms the presence of mobile genetic elements and plethora of degradation genes and pathways making them a potential candidate for bioremediation. Beside genome wide predictions there are number of experimental evidences confirm the degradation potential of bacteria belonging to genus Sphingopyxis and also the production of different secondary metabolites that help them interact and survive in their ecological niches. This review provides detailed information on ecology, general characteristic and the significant implications of Sphingopyxis species in environmental management along with the bio-synthetic potential.

Characteristics of microbial denitrification under different aeration intensities: Performance, mechanism, and co-occurrence network

This study aimed to explore how dissolved oxygen (DO) affected the characteristics and mechanisms of denitrification in mixed bacterial consortia. We analyzed denitrification efficiency, intracellular nicotinamide adenine dinucleotide (NADH), relative expression of functional genes, and potential co-occurrence network of microorganisms. Results showed that the total nitrogen (TN) removal rates at different aeration intensities (0.00, 0.25, 0.63, and 1.25 L/(L·min)) were 0.93, 1.45, 0.86, and 0.53 mg/(L·min), respectively, which were higher than previously reported values for pure culture. The optimal aeration intensity was 0.25 L/(L·min), at which the maximum NADH accumulation rate and highest relative abundance of napA, nirK, and nosZ were achieved. With increased aeration intensity, the amount of electron flux to nitrate decreased and nitrate assimilation increased. On one hand, nitrate reduction was primarily inhibited by oxygen through competition for electron donors of a certain single strain. On the other hand, oxygen was consumed rapidly by bacteria by stimulating carbon metabolism to create an optimal denitrification niche for denitrifying microorganisms. Denitrification was performed via inter-genus cooperation (competitive interactions and symbiotic relationships) between keystone taxa (Azoarcus, Paracoccus, Thauera, Stappia, and Pseudomonas) and other heterotrophic bacteria (OHB) in aeration reactors. However, in the non-aeration case, which was primarily carried out based on intra-genus syntrophy within genus Propionivibrio, the co-occurrence network constructed the optimal niche contributing to the high TN removal efficiency. Overall, this study enhanced our knowledge about the molecular ecological mechanisms of aerobic denitrification in mixed bacterial consortia and has theoretical guiding significance for further practical application.

Transfer of Sphingorhabdus marina, Sphingorhabdus litoris, Sphingorhabdus flavimaris and Sphingorhabdus pacifica corrig. into the novel genus Parasphingorhabdus gen. nov. and Sphingopyxis baekryungensis into the novel genus Novosphingopyxis gen. nov. within the family Sphingomonadaceae

During a phylogenetic analysis of Sphingorhabdus and its closely related genera in the family Sphingomonadaceae, we found that the genus Sphingorhabdus and the species Sphingopyxis baekryungensis might not be properly assigned in the taxonomy. Phylogenetic, phenotypic and chemotaxonomic characterizations clearly showed that the genus Sphingorhabdus should be reclassified into two genera (Clade I and Clade II), for which the original genus name, Sphingorhabdus, is proposed to be retained only for Clade I, and a new genus named as Parasphingorhabdus gen. nov. is proposed for Clade II with four new combinations: Parasphingorhabdus marina comb. nov., Parasphingorhabdus litoris comb. nov., Parasphingorhabdus flavimaris comb. nov. and Parasphingorhabdus pacifica comb. nov. Moreover, Sphingopyxis baekryungensis should represent a novel genus in the family Sphingomonadaceae, for which the name Novosphingopyxis gen. nov. is proposed, with a combination of Novosphingopyxis baekryungensis comb. nov. The study provides a new insight into the taxonomy of closely related genera in the family Sphingomonadaceae.

Sphingorhabdus soli sp. nov., isolated from Arctic soil

A Gram-stain-negative, strictly aerobic, rod-shaped and non-motile bacterial strain, designated D-2Q-5-6^T, was isolated from a soil sample collected from the Arctic region. Strain D-2Q-5-6^T was found to grow at 10-43 °C (optimum, 28 °C), at pH 6.0-9.0 (pH 7.0) and in 0-5 % (w/v) NaCl (0-1 %). Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain D-2Q-5-6^T fell into the genus Sphingorhabdus and shared less than 95.8 % identity with all type strains of recognized species of this genus. The major cellular fatty acids of strain D-2Q-5-6^T were summed feature 8 (C_18 : 1 ω7c and/or C_18 : 1 ω6c; 31.4 %), summed feature 3 (C_16 : 1 ω7c and/or C_16 : 1 ω6c; 26.8 %) and C_14 : 0 2OH (11.7 %). The polar lipids consisted of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylcholine and sphingoglycolipid. The predominant quinone was identified as Q10. The DNA G+C content of strain D-2Q-5-6^T was 64.5 mol%. Based on the results of phylogenetic analysis and distinctive phenotypic characteristics, strain D-2Q-5-6^T is concluded to represent a novel species of the genus Sphingorhabdus, for which the name Sphingorhabdus soli sp. nov. is proposed. The type strain of the species is D-2Q-5-6^T (=MCCC 1A06070^T=KCTC 52311^T).

Sphingorhabdus lacus sp. nov. and Sphingorhabdus profundilacus sp. nov., isolated from freshwater environments

Two Gram-stain-negative, aerobic, non-motile bacteria, designated IMCC1753^T and IMCC26285^T, were isolated from a shallow eutrophic pond and a deep oligotrophic lake, respectively. Results of 16S rRNA gene sequence analysis indicated that the two strains shared 99.8 % sequence similarity and were most closely related to Sphingorhabdus contaminans JC216^T(98.7-98.8 %). The whole genome sequences of strains IMCC1753^T and IMCC26285^T were 3.5 and 2.9 Mbp in size with 56.6 and 55.5 mol% DNA G+C content, respectively. Average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between the two strains were 82.2 and 25.8 %, respectively, indicating that they are separate species. The two strains showed ≤98.8 % 16S rRNA gene sequence similarities and ≤82.2 % ANI and ≤28.7 % dDDH values to closely related species of the genus Sphingorhabdus, indicating that the two strains each represent novel species. Major fatty acid constituents of strain IMCC1753^T were C_17 : 1  ω6c, C_17 : 1  ω8c and summed features 3 (C_16 : 1  ω6c and/or C_16 : 1  ω7c) and 8 (C_18 : 1  ω6c and/or C_18 : 1  ω7c); those of strain IMCC26285^T were summed features 3 and 8. The predominant isoprenoid quinone detected in both strains was ubiquinone-10 and the most abundant polyamine was spermidine. Both strains contained phosphatidylethanolamine, phosphatidylmethylethanolamine, phosphatidylcholine, phosphatidylglycerol, diphosphatidylglycerol and sphingoglycolipid as major polar lipids. On the basis of the phylogenetic and phenotypic characteristics, strains IMCC1753^T and IMCC26285^T were considered to represent two distinct novel species in the genus Sphingorhabdus, for which the names Sphingorhabdus lacus (IMCC1753^T=KCTC 52480^T=KACC 18985^T=NBRC 112442^T) and Sphingorhabdus profundilacus (IMCC26285^T=KCTC 52479^T=KACC 18986^T=NBRC 112454^T) are proposed, respectively.

Draft Genome Sequence of Sphingorhabdus sp. Strain EL138, a Metabolically Versatile Alphaproteobacterium Isolated from the Gorgonian Coral Eunicella labiata

Here, we report the draft genome sequence of Sphingorhabdus sp. strain EL138, an alphaproteobacterium that shows potential to degrade polycyclic aromatic compounds and to cope with various heavy metals and antibiotics. Moreover, the strain, isolated from the gorgonian coral Eunicella labiata, possesses several genes involved in the biosynthesis of polyphosphates, polyketides, and terpenoids.