Paracoccus sordidisoli sp. nov., isolated from an agricultural field contaminated with hexachlorocyclohexane isomers

Syngas-driven sewage sludge conversion to microbial protein through H2S- and CO-tolerant hydrogen-oxidizing bacteria

Treating excess municipal sewage sludge (MSS) by means of thermochemical processes could enable its conversion into high-value microbial protein (MP) through syngas. Nevertheless, the variable composition and content of inhibitory compounds of the latter hinders the application potential of such a biorefinery scheme. Through a series of short- (48 to 96 h) and long-term (30 days) batch aerobic bioconversion tests, the present study aimed at investigating the potential of a mixed culture of hydrogen-oxidizing bacteria (HOB) to produce MP from a simulated syngas mixture characterized by variable H2 and CO2 concentrations, and different levels of CO and H2S as potential inhibitors of the HOB-driven process. Syngas was converted into MP with a protein content as high as 74 %, reaching biomass yields of 0.25 g VSS/g H2-COD, close to the maximum reported HOB yield of 0.28 g VSS/g H2-COD,  and volumetric productivities of 16 mg VSS/L/h. The potential of the process to provide between 50 and 100 % of the total nitrogen requirement of HOB solely by means of the gaseous ammonia nitrogen recovered through syngas was also preliminarily calculated. The presence of H2S and CO concentrations up to 0.4 % and up to 40 %, respectively, and a wide range of H2/CO2 ratios (2 - 10) had no negative influence on the main process performances. The role played by H2S- and CO-tolerant HOB species was fundamental to guarantee a high tolerance to microbial inhibitors, and demonstrated the high potential of mixed cultures for resource recovery and valorisation.

Bioremediation characteristics, influencing factors of dichlorodiphenyltrichloroethane (DDT) removal by using non-indigenous Paracoccus sp

The marine bacterium able to consume DDT as the nutrient source was isolated from sea water which was identified as Paracoccus sp. DDT-21 based on 16 S rDNA gene sequence and Gram negative rod, obligate aerobic, non-motile biochemical characteristics. The isolate can degrade over 80% of the DDT, at a concentration of 50 mg/L in MSM in 72 h. Time and pollutant (DDT) dependent growth studies indicated that the isolate Paracoccus sp., DDT-21 significantly degrade the DDT and tolerates under DDT stress up to 50 mg/L. The DDT degradation capability of the strain Paracoccus sp. DDT-21 was found to be 5 ˃ 10 ˃ 15 ˃ 25 ˃ 50 mg/L DDT. The high concentrations (75 and 100 mg/L) of DDT showed significant decrease in DDT degradation. The optimal DDT degradation (∼90.0%) was observed at 6 g/L of yeast extract, 6% of glucose in pH 7.0 at 35 °C with 72 h of incubation as constant. Furthermore, four metabolites were observed by GC-MS analysis such as, DDE, DDD, DDMU, and DDA. The obtained results indicate that the isolate Paracoccus sp. DDT-21 is a promising candidate for the removal and/or detoxification of DDT in the environment.

Pectin Degradation is an Important Determinant for Alfalfa Silage Fermentation through the Rescheduling of the Bacterial Community

This study aimed to evaluate the effects of the four kinds of additives on the silage quality and the relevant bacterial community diversity by Illumina HiSeq 16S rRNA sequencing. The four kinds of additives were Lactobacillus plantarum (LP), organic acids including gallic acid (GA) and phenyllactic acid (PA), pectin (PEC), and enzymes including pectinase (PEE) and cellulase (CE). After 30 d of fermentation, the pH value was shown to have the lowest value in the PEE and PEC groups, followed by the PA group, and then in CE and GA groups; the highest value of pH was found in both LP and control groups. The ammonia nitrogen concentration was lower in the PEE group compared to the other groups except for the PA group. In the comparisons among the seven groups, Lactobacillus was higher in the LP group, Paracoccus was higher in the GA group, Weissella was higher in the PA group, Leuconostoc was higher in the PEC group, Bacillus, Aeromonas, and Curvibacter were higher in the PEE group, and Coriobacteriaceae_UCG_002 was higher in the CE group compared to the other groups. This study proposed that the addition of PEC and PEE improved the fermentation quality of alfalfa silage compared to other additives by improving the bacterial community of Leuconostoc, and Bacillus and Aeromonas, respectively. Moreover, the enhanced fermentation quality of alfalfa silage by the supplementation of PEC and PEE might be attributed to other unclassified genera. This study provides an implication that pectin degradation is an important determinant for alfalfa silage fermentation through the rescheduling of bacterial community diversity.

Complete genome sequence of Paracoccus sp. strain AK26: Insights into multipartite genome architecture and methylotropy

The present study reports the functional annotation of complete genome of methylotrophic bacterium Paracoccus sp. strain AK26. The 3.6 Mb genome with average GC content of 65.7% was distributed across five replicons; including chromosome (2.7 Mb) and four extrachromosomal replicons pAK1 (471Kb), pAK2 (189Kb), pAK3 (129Kb) and pAK4 (84 Kb). Interestingly, nearly 23% of the Cluster of Orthologous Group (COG) of proteins were annotated on extrachromosomal replicons and 185Kb genome content was attributed to segregated 19 genomic island regions. Among the four replicons, pAK4 was identified as essential and integral part of the genome, as supported by codon usage, GC content (66%) and synteny analysis. Comparative genome analysis for methylotrophy showed mechanistic variations in oxidation and assimilation of C1 compounds among closely related Paracoccus spp. Collectively, present study reports the functional characterization and genomic architecture of strain AK26 and provides genetic basis for quinone and isoprenoid based secondary metabolites synthesis using strain AK26.

Paracoccus jeotgali sp. nov., isolated from Korean salted and fermented shrimp

A Gram-stain-negative and facultatively aerobic bacterium, designated as strain CBA4604^T, was isolated from a traditional Korean salted and fermented shrimp food (saeu-jeot). Phylogenetic analysis based on 16S rRNA gene sequences showed that strain CBA4604^T formed a clearly distinct phyletic lineage from closely related species within the genus Paracoccus. Strain CBA4604^T was the most closely related to P. koreensis Ch05^T (97.5% 16S rRNA gene sequence similarity) and other type strains (≤ 97.0%). The genome comprised a chromosome and two plasmids of 3,299,166 bp with 66.5% G+C content. The DNA-DNA relatedness values between strain CBA4604^T and P. koreensis Ch05^T, P. alcaliphilus DSM 8512^T, and P. stylophorae KTW-16^T were 30.5%, 22.9%, and 16.7%, respectively. Cells of the strain were short rod-shaped and oxidase- and catalase-positive. The growth of strain CBA-4604^T was observed at 10-40°C (optimum, 37°C), pH 6.0-10.0 (optimum, pH 7.0), and in the presence of 0-8.0% (w/v) NaCl (optimum, 0-2.0%). Strain CBA4604^T contained ubiquinone 10 as the sole isoprenoid quinone and summed feature 8 (C_18:1ω7c/C_18:1ω6c) and C_18:0 as the major cellular fatty acids. The polar lipids consisted of phosphatidylcholine, phosphatidylglycerol, diphosphatidylglycerol, phospholipid, an unidentified aminolipid, an unidentified glycolipid, and three unidentified lipids. Based on its phylogenetic, genomic, phenotypic, and chemotaxonomic features, we concluded that strain CBA-4604^T represents a novel species in the genus Paracoccus and we propose the name Paracoccus jeotgali sp. nov. The type strain is CBA4604^T (= KACC 19579^T = JCM 32510^T).

Paracoccus alimentarius sp. nov., isolated from a Korean foodstuff, salted pollack

A Gram-stain-negative, aerobic, non-motile and coccoid or ovoid bacterial strain, designated LB2^T, was isolated from a Korean foodstuff, salted pollack. Strain LB2^T grew optimally at 25-30 °C, at pH 7.0-8.0 and in the presence of 0-2.0 % (w/v) NaCl. Phylogenetic trees based on 16S rRNA gene sequences showed that strain LB2^T belonged to the genus Paracoccus, coherently clustering with the type strain of Paracoccus sulfuroxidans. Strain LB2^T exhibited 16S rRNA gene sequence similarity values of 98.0 and 97.0 % to the type strains of P. sulfuroxidans and Paracoccus halophilus, respectively, and of less than 96.9 % to the type strains of other Paracoccus species. Strain LB2^T contained Q-10 as the predominant ubiquinone. Major fatty acids of strain LB2^T were cyclo C19 : 0ω8c, C18 : 1ω7c and C16 : 0 (when grown on MA) or C18 : 1ω7c and C16 : 0 (on TSA). The major polar lipids detected in strain LB2^T were phosphatidylcholine, phosphatidylglycerol, diphosphatidylglycerol, one unidentified aminolipid and one unidentified glycolipid. The DNA G+C content of strain LB2^T was 61.4 mol% and its DNA-DNA relatedness values with the type strains of P. sulfuroxidans and P. halophilus were 26 and 18 %, respectively. Differential phenotypic properties, together with its phylogenetic and genetic distinctiveness, revealed that strain LB2^T is separated from recognized Paracoccus species. On the basis of the data presented, strain LB2^T is considered to represent a novel species of the genus Paracoccus, for which the name Paracoccus alimentarius sp. nov. is proposed. The type strain is LB2^T (=KCTC 62138^T=NBRC 113023^T).