Additional Role of Nicotinic Acid Hydroxylase for the Transformation of 3-Succinoyl-Pyridine by Pseudomonas sp. Strain JY-Q

Abstract

Nicotine and nicotinic acid (NA) are both considered to be representatives of N-heterocyclic aromatic compounds, and their degradation pathways have been revealed in Pseudomonas species. However, the co-occurrence of these two pathways is only observed in Pseudomonas sp. JY-Q. Nicotine pyrrolidine catabolism pathway of strain JY-Q consists of function modules Nic1, Spm, and Nic2. The module enzyme, 3-succinoylpyridine monooxygenases (Spm), catalyzes transformation of 3-succinoyl-pyridine (SP) to 6-hydroxy-3-succinoyl-pyridine (HSP). There exist two homologous but not identical Spm (namely Spm1 and Spm2) in JY-Q. However, when spm1 and spm2 both were in-frame deleted, the mutant still grew well in the basic salt medium supplemented with nicotine as the sole carbon/nitrogen nutrition, suggesting that there exists an alternative pathway responsible for SP catabolism in JY-Q. NicAB, an enzyme accounting for NA hydroxylation, contains re-organized domains similar to that of Spm. When JY-Q_nicAB gene was introduced into another Pseudomonas strain, which is unable to degrade NA, the resultant recombinant strain exhibited the ability transforming SP to HSP except the ability NA metabolism. Here, we ccan conclude that NicAB in strain JY-Q exhibits an additional role of SP transforming. The other genes in NA cluster, NicXDFE (Nic2 homolog), then also exhibit the role of HSP subsequent metabolism for energy yield. This finding also suggests that the co-occurrence of nicotine and NA degradation genes in strain JY-Q represents a contribution for JY-Q making it more effective and flexible for the degradation of nicotine. Importance 3-Succinoyl-pyridine (SP) and 6-hydroxy-3-succinoyl-pyridine (HSP) both are valuable chemical precursors to produce insecticides and hypotensive agents. SP and HSP could be renewable through the nicotine microbial degradation pathway in which 3-succinoylpyridine monooxygenases (Spm) account for transforming SP into HSP in Pseudomonas sp. JY-Q. However, when two homologous Spm genes (spm1 and spm2) were knocked out, the mutant kept the ability to degrade nicotine. Thus, in addition to Spm, JY-Q should have alternative pathway for SP conversion. In this research, we showed that JY-Q_NicAB was responsible for this alternative SP conversion. Both of the primary functions for nicotinic acid dehydrogenation and the additional function for SP metabolism were detected in a recombinant strain harboring JY-Q_NicAB. As a result, both nicotinic acid and nicotine degradation pathways in JY-Q contribute to its remarkable nicotine tolerance and nicotine degradation availability. These findings also provide one more metabolic engineering strategy for accumulation for value-added intermediates.

Effects of Bacillus altitudinis inoculants on cigar tobacco leaf fermentation

“…Additionally, significantly active nicotinate and nicotinamide metabolism in the inoculant-rich fermentation (BA_1, p < 0.001, Figure 3 ) was observed. It should be noted that nicotine degradation products were in the same metabolic pathway as the syntheses of nicotinate, nicotinamide, and nicotinamide adenine dinucleotide (NAD + ) ( Li et al, 2021 ), and so, nicotine continuously transformed in CTLs to nicotinate, nicotinamide, and NAD + in BA_1 had a positive effect on the microflora energy metabolism and cigar products. Meanwhile, although phosphate was added to the inoculants, the inositol phosphate metabolism pathway was still significantly upregulated ( p < 0.001), indicating that the supply of phosphate might be still a limiting factor in the system after the first fermentation.…”

“…Additionally, the addition of inoculants enhanced the contribution rate of nicotinate and nicotinamide metabolism by Corynebacterium to 50.49% in BA_2 ( Figure 4 ) and improved the Corynebacterium abundance in BA_3 to 21.29%, which was 31 times higher than that of CK_3 (0.68%; Figure 2B ). The results suggested that under the addition of inoculants (BA group), nicotine degradation-associated NAD + synthesis ( Yu et al, 2015 ; Li et al, 2017 ; Li et al, 2021 ), NAD + /NADH redox equilibrium, and NADH-involved energy metabolism in Corynebacterium were more advantageous than that in Staphylococcus . Accordingly, the contribution rate of nicotine degradation and NAD + anabolism by Staphylococcus in CK_2 was significantly decreased by 57% compared with the inoculant group (BA_2; Figure 4 ), identifying the positive roles of Corynebacterium in nicotine degradation for the first time.…”

Comamonas resistens sp. nov. and Pseudomonas triclosanedens sp. nov., two members of the phylum Pseudomonadota isolated from the wastewater treatment system of a pharmaceutical factory

“…Members of the genus Pseudomonas are widely distributed, metabolically versatile, and important for recycling elements in the environment [23, 24]. They are also lauded for their prominent role in environmental remediation, including the biodegradation of polycyclic aromatic hydrocarbons [25], petroleum [26], neonicotinoid insecticides [27], chlorinated phenols [28] and PPCPs [29]. In this study, three novel pollutant-degrading strains (ZM23 T , ZM24 and ZM25) were subjected to a polyphasic approach for comparison with the type strains of the genus Pseudomonas , together with an analysis of their genomic characteristics associated with the biodegradation of aromatic pollutants.…”