Complete degradation of di-n-butyl phthalate by Glutamicibacter sp. strain 0426 with a novel pathway

Degradation efficiency for phthalates and cooperative mechanism in synthetic bacterial consortium and its bioaugmentation for soil remediation

Agricultural soil contamination by phthalates (PAEs) necessitates efficient remediation strategies with microbial degradation. However, microbial cooperation of PAE-degrading consortia and their effectiveness in bioaugmentation through re-colonization remain poorly understood. In this study, synthetic PAE-degrading bacterial consortia were constructed using the 20 isolates derived from maize rhizosphere to explore microbial cooperation and bioaugmentation for PAE removal. Following optimization, five key isolates either with strong individual degradation capacity or beneficial metabolic interactions were co-cultured to form a synthetic consortium SC-5. This consortium demonstrated efficient degradation of di-n-butyl phthalate (DBP) and di-(2-ethylhexyl) phthalate (DEHP) (each at 200 mg/L), achieving 98.1 %-100 % removal percentages and reduced half-lives compared to the single strain. Metabolic pathway analysis revealed that consortium SC-5 could completely degrade PAEs and their intermediates including monoester, phthalic acid, and protocatechuate through cooperative metabolism. Within the consortium, Mycobacterium sp. R14 exhibited strong PAE-degrading ability, while genera Rhizobium and Paenarthrobacter predominated in mineral salt media supplemented with PAEs or glucose, as confirmed by high-throughput sequencing. These results underscore their differentiated utilization of parent PAEs, degradation intermediates, and metabolites through microbial cooperation. Furthermore, consortium SC-5 could effectively re-colonize maize rhizosphere with significantly higher relative abundances of the genera affiliating to the members of SC-5 than those in bulk soil, thereby significantly facilitating DEHP removal from rhizosphere. The present study highlights the importance of microbial cooperation within synthetic consortium and demonstrates its potential in bioaugmentation-based bioremediation of PAE-polluted soil.

Proposal of Crystallibacter gen. nov., Crystallibacter permensis sp. nov. and Crystallibacter degradans sp. nov. for the salt-tolerant and aromatics degrading actinobacteria, and reclassification of Arthrobacter crystallopoietes as Crystallibacter crystallifaciens comb. nov

Four salt-tolerant and aromatics degrading strains used in this study were isolated from polluted technogenic soil on the territory of the Verkhnekamsk potash deposit (Russia). The strains were aerobic, Gram-stain-positive, non-motile, non-endospore-forming irregular rods, exhibiting a marked rod-coccus growth cycle. They contained lysine-based peptidoglycan, teichulosonic acid and poly(glycosyl phosphate) polymers in the cell walls. The major menaquinone was MK-9(H2), the predominant fatty acids were saturated, anteiso- and iso-branched, and the major compounds of polar lipid profiles included phosphatidylglycerol, diphosphatidylglycerol, phosphatidylinositol and two glycolipids (monogalactosyldiacylglycerol and dimannosylglyceride). The strains showed the highest 16S rRNA gene sequence similarity to Arthrobacter crystallopoietes (99.6-99.9%), followed by A. mangrovi (98.3-98.5%) and A. globiformis, the type species of the genus Arthrobacter (97.6-97.8%). The values of overall genome related indices (ANI, dDDH, AAI and POCP) indicated that the target strains and A. crystallopoietes represented three species within a new genus. These species clearly differed from each other and from A. mangrovi and A. globiformis in the phenotypic traits, including the peptidoglycan type and the structures and compositions of cell wall glycopolymers. Based on the findings of this study and the previously published data, we provide the description of the new genus Crystallibacter gen. nov. with the type species Crystallibacter crystallifaciens comb. nov. (type strain, VKM Ac-1107 T) and two newly revealed species, Crystallibacter permensis sp. nov. (type strain, B905T = VKM Ac-2550T = LMG 33113T) and Crystallibacter degradans sp. nov. (type strain, SF27T = VKM Ac-2063T = LMG 33112T).

Comparative genomics based exploration of xenobiotic degradation patterns in Glutamicibacter, Arthrobacter, and Pseudarthrobacter isolated from diverse ecological habitats

Xenobiotics pose a substantial threat to environmental integrity by disrupting normal ecosystems. The genus Arthrobacter, known for its metabolic versatility can degrade several xenobiotic compounds. Arthrobacter strains have also undergone frequent taxonomic revisions and reclassifications to strains including Pseudarthrobacter and Glutamicibacter. Here, we present the complete genome sequence of Glutamicibacter protophormiae strain NG4, isolated from a coastal area surrounded by chemical plants. Further, through comparative genomics involving 55 strains from Glutamicibacter, Arthrobacter, and Pseudarthrobacter, we elucidated taxonomic relationships and xenobiotic degradation potential. Our genomics-based findings revealed a generally even distribution of xenobiotic-degrading genes and pathways among the studied strains. Glutamicibacter species emerged as potential candidate for steroid degradation. A significant number of host-specific and environmental isolates predominantly possessed pathways for 4-hydroxybenzoate (4-HB) degradation and only the environmental isolates possessed benzoate degradation pathway. Certain Arthrobacter and Pseudarthrobacter species isolated from the environmental settings were identified as potential degraders of toluene, xylene, and phenanthrene. Notably, most strains contained pathways for azathioprine, capecitabine, and 5-fluorouridine pharmaceutical drug metabolism. Overall, our findings shed light on microbial metabolic diversity among 55 strains isolated from diverse sources and hint the importance of strict environmental monitoring. Further, for the application of the putative xenobiotic degrading strains, experimental validation is required in the future.

Elucidation of 4-Hydroxybenzoic Acid Catabolic Pathways in Pseudarthrobacter phenanthrenivorans Sphe3

4-hydroxybenzoic acid (4-HBA) is an aromatic compound with high chemical stability, being extensively used in food, pharmaceutical and cosmetic industries and therefore widely distributed in various environments. Bioremediation constitutes the most sustainable approach for the removal of 4-hydroxybenzoate and its derivatives (parabens) from polluted environments. Pseudarthrobacter phenanthrenivorans Sphe3, a strain capable of degrading several aromatic compounds, is able to grow on 4-HBA as the sole carbon and energy source. Here, an attempt is made to clarify the catabolic pathways that are involved in the biodegradation of 4-hydroxybenzoate by Sphe3, applying a metabolomic and transcriptomic analysis of cells grown on 4-HBA. It seems that in Sphe3, 4-hydroxybenzoate is hydroxylated to form protocatechuate, which subsequently is either cleaved in ortho- and/or meta-positions or decarboxylated to form catechol. Protocatechuate and catechol are funneled into the TCA cycle following either the β-ketoadipate or protocatechuate meta-cleavage branches. Our results also suggest the involvement of the oxidative decarboxylation of the protocatechuate peripheral pathway to form hydroxyquinol. As a conclusion, P. phenanthrenivorans Sphe3 seems to be a rather versatile strain considering the 4-hydroxybenzoate biodegradation, as it has the advantage to carry it out effectively following different catabolic pathways concurrently.