The FabA-FabB Pathway Is Not Essential for Unsaturated Fatty Acid Synthesis but Modulates Diffusible Signal Factor Synthesis in Xanthomonas campestris pv. campestris.

Most bacteria use type II fatty acid synthesis (FAS) systems for synthesizing fatty acids, of which the conserved FabA-FabB pathway is considered to be crucial for unsaturated fatty acid (UFA) synthesis in gram-negative bacteria. Xanthomonas campestris pv. campestris, the phytopathogen of black rot disease in crucifers, produces higher quantities of UFAs under low-temperature conditions for increasing membrane fluidity. The fabA and fabB genes were identified in the X. campestris pv. campestris genome by BLAST analysis; however, the growth of the X. campestris pv. campestris fabA and fabB deletion mutants was comparable to that of the wild-type strain in nutrient and minimal media. The X. campestris pv. campestris ΔfabA and ΔfabB strains produced large quantities of UFAs and, altogether, these results indicated that the FabA-FabB pathway is not essential for growth or UFA synthesis in X. campestris pv. campestris. We also observed that the expression of X. campestris pv. campestris fabA and fabB restored the growth of the temperature-sensitive Escherichia coli fabA and fabB mutants CL104 and CY242, respectively, under non-permissive conditions. The in-vitro assays demonstrated that the FabA and FabB proteins of X. campestris pv. campestris catalyzed FAS. Our study also demonstrated that the production of diffusible signal factor family signals that mediate quorum sensing was higher in the X. campestris pv. campestris ΔfabA and ΔfabB strains and greatly reduced in the complementary strains, which exhibited reduced swimming motility and attenuated host-plant pathogenicity. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.

Intervention Effect of Mindfulness-Based Mental Health Education Therapy on Adolescents Mobile Phone Addiction and Cognitive Tendency.

Background: Teenagers are more prone to mobile phone addiction than other age groups due to their lack of self-control. This addiction to mobile phones severely affects their physical and mental health, causing irreversible harm as they grow older. As such, exploring suitable psychotherapy for their physical and mental development needs is essential, in ways that effectively change teenagers' mobile phone addictive behaviors. Methods: An experimental study was conducted on 910 teenage volunteers recruited from 5 communities in Gansu, Hebei, and Liaoning Provinces in China from May to July 2023. The participants were screened using the Mobile Phone Addiction Index Scale (MPAI). On the basis of the evaluation results, 56 individuals were selected based on the evaluation results and randomly divided into experimental and control groups, each comprising 28 individuals. The experimental group underwent an 8-week mindfulness-based mental health education therapy. Both groups were measured before and after the intervention. Results: The mobile phone addiction score of the experimental group was significantly lower than that of the control group (P<0.001). The cognitive tendency score and mental wellbeing score of the experimental group was significantly higher than those of the control group (P<0.001). Conclusion: Mindfulness-based mental health education therapy effectively alleviates teenagers' mobile phone addiction and improves their cognitive tendencies and mental health. This approach serves as a valuable reference for effectively preventing and managing mobile phone addiction among teenagers.

Protective effect of total flavonoids from Ixeris Sonchifolia on herpes simplex virus keratitis in mice.

BACKGROUND: To investigate the protective effect of Ixeris Sonchifolia (Bae.) Hance (ISH) extract on herpes simplex virus keratitis (HSK) in mice. METHODS: A mouse model of HSK was established by inoculating 60 mice (60 right eyes) with herpes simplex virus type 1 (HSV-1) by corneal scratch. The other 15 mice as blank control only received corneal scratch but without HSV-1. From the 2nd day after the successful modeling, the experimental group was fed with ISH total flavonoids (50, 100 and 200 mg/kg) orally, twice a day for 14 days. The model group and control group were given the same amount of normal saline. The pathological changes of cornea were observed once a day by slit lamp microscopy combined with fluorescein staining. The corneal histopathological examination, the survival status and the serum levels of interleukin-2 (IL-2), IL-4 and interferon-gama (INF-γ) were performed at the end of the experiment. RESULTS: The result showed that ISH could significantly improve the corneal lesion degree, increase mice survival rate, and markedly increase the levels of IL-2 and INF-γ, reduce the levels of IL-4 in serum of mice. CONCLUSIONS: ISH could increase the anti-virus ability, promote the healing of corneal inflammation and alleviate the pathological damage of cornea, which suggested that ISH has a potential and valuable therapeutic effect on the HSK.

Mikania micrantha genome provides insights into the molecular mechanism of rapid growth.

Mikania micrantha is one of the top 100 worst invasive species that can cause serious damage to natural ecosystems and substantial economic losses. Here, we present its 1.79 Gb chromosome-scale reference genome. Half of the genome is composed of long terminal repeat retrotransposons, 80% of which have been derived from a significant expansion in the past one million years. We identify a whole genome duplication event and recent segmental duplications, which may be responsible for its rapid environmental adaptation. Additionally, we show that M. micrantha achieves higher photosynthetic capacity by CO2 absorption at night to supplement the carbon fixation during the day, as well as enhanced stem photosynthesis efficiency. Furthermore, the metabolites of M. micrantha can increase the availability of nitrogen by enriching the microbes that participate in nitrogen cycling pathways. These findings collectively provide insights into the rapid growth and invasive adaptation.

Central 5-hydroxytryptamine (5-HT) mediates colonic motility by hypothalamus oxytocin-colonic oxytocin receptor pathway.

Gut-derived 5-hydroxytryptamine (5-HT) is well known for its role in mediating colonic motility function. However, it is not very clear whether brain-derived 5-HT is involved in the regulation of colonic motility. In this study, we used central 5-HT knockout (KO) mice to investigate whether brain-derived 5-HT mediates colonic motility, and if so, whether it involves oxytocin (OT) production in the hypothalamus and OT receptor in the colon. Colon transit time was prolonged in KO mice. The OT levels in the hypothalamus and serum were decreased significantly in the KO mice compared to wild-type (WT) controls. OT increased colonic smooth muscle contraction in both KO and WT mice, and the effects were blocked by OT receptor antagonist and tetrodotoxin but not by hexamethonium or atropine. Importantly, the OT-induced colonic smooth muscle contraction was decreased significantly in the KO mice relative to WT. The OT receptor expression of colon was detected in colonic myenteric plexus of mice. Central 5-HT is involved in the modulation of colonic motility which may modulate through its regulation of OT synthesis in the hypothalamus. Our results reveal a central 5-HT - hypothalamus OT - colonic OT receptor axis, providing a new target for the treatment of brain-gut dysfunction.

Novel Xanthomonas campestris Long-Chain-Specific 3-Oxoacyl-Acyl Carrier Protein Reductase Involved in Diffusible Signal Factor Synthesis.

The precursors of the diffusible signal factor (DSF) family signals of Xanthomonas campestris pv. campestris are 3-hydroxyacyl-acyl carrier protein (3-hydroxyacyl-ACP) thioesters having acyl chains of 12 to 13 carbon atoms produced by the fatty acid biosynthetic pathway. We report a novel 3-oxoacyl-ACP reductase encoded by the X. campestris pv. campestris XCC0416 gene (fabG2), which is unable to participate in the initial steps of fatty acyl synthesis. This was shown by the failure of FabG2 expression to allow growth at the nonpermissive temperature of an Escherichia colifabG temperature-sensitive strain. However, when transformed into the E. coli strain together with a plasmid bearing the Vibrio harveyi acyl-ACP synthetase gene (aasS), growth proceeded, but only when the medium contained octanoic acid. In vitro assays showed that FabG2 catalyzes the reduction of long-chain (≥C8) 3-oxoacyl-ACPs to 3-hydroxyacyl-ACPs but is only weakly active with shorter-chain (C4, C6) substrates. FabG1, the housekeeping 3-oxoacyl-ACP reductase encoded within the fatty acid synthesis gene cluster, could be deleted in a strain that overexpressed fabG2 but only in octanoic acid-supplemented media. Growth of the X. campestris pv. campestris ΔfabG1 strain overexpressing fabG2 required fabH for growth with octanoic acid, indicating that octanoyl coenzyme A is elongated by X. campestris pv. campestrisfabH Deletion of fabG2 reduced DSF family signal production, whereas overproduction of either FabG1 or FabG2 in the ΔfabG2 strain restored DSF family signal levels.IMPORTANCE Quorum sensing mediated by DSF signaling molecules regulates pathogenesis in several different phytopathogenic bacteria, including Xanthomonas campestris pv. campestris DSF signaling also plays a key role in infection by the human pathogen Burkholderia cepacia The acyl chains of the DSF molecules are diverted and remodeled from a key intermediate of the fatty acid synthesis pathway. We report a Xanthomonas campestris pv. campestris fatty acid synthesis enzyme, FabG2, of novel specificity that seems tailored to provide DSF signaling molecule precursors.

Inefficient translation renders the Enterococcus faecalis fabK enoyl-acyl carrier protein reductase phenotypically cryptic.

Enoyl-acyl carrier protein (ACP) reductase catalyzes the last step of the bacterial fatty acid elongation cycle. Enterococcus faecalis is unusual in that it encodes two unrelated enoyl-ACP reductases, FabI and FabK. We recently reported that deletion of the gene encoding FabI results in an unsaturated fatty acid (UFA) auxotroph despite the presence of fabK, a gene encoding a second fully functional enoyl-ACP reductase. By process of elimination, our prior report argued that poor expression was the reason that fabK failed to functionally replace FabI. We now report that FabK is indeed poorly expressed and that the expression defect is at the level of translation rather than transcription. We isolated four spontaneous mutants that allowed growth of the E. faecalis ΔfabI strain on fatty acid-free medium. Each mutational lesion (single base substitution or deletion) extended the fabK ribosome binding site. Inactivation of fabK blocked growth, indicating that the mutations acted only on fabK rather than a downstream gene. The mutations activated fabK translation to levels that supported fatty acid synthesis and hence cell growth. Furthermore, site-directed and random mutagenesis experiments showed that point mutations that resulted in increased complementarity to the 3' end of the 16S rRNA increased FabK translation to levels sufficient to support growth, whereas mutations that decreased complementarity blocked fabK translation.

The two functional enoyl-acyl carrier protein reductases of Enterococcus faecalis do not mediate triclosan resistance.

UNLABELLED: Enoyl-acyl carrier protein (enoyl-ACP) reductase catalyzes the last step of the elongation cycle in the synthesis of bacterial fatty acids. The Enterococcus faecalis genome contains two genes annotated as enoyl-ACP reductases, a FabI-type enoyl-ACP reductase and a FabK-type enoyl-ACP reductase. We report that expression of either of the two proteins restores growth of an Escherichia coli fabI temperature-sensitive mutant strain under nonpermissive conditions. In vitro assays demonstrated that both proteins support fatty acid synthesis and are active with substrates of all fatty acid chain lengths. Although expression of E. faecalis fabK confers to E. coli high levels of resistance to the antimicrobial triclosan, deletion of fabK from the E. faecalis genome showed that FabK does not play a detectable role in the inherent triclosan resistance of E. faecalis. Indeed, FabK seems to play only a minor role in modulating fatty acid composition. Strains carrying a deletion of fabK grow normally without fatty acid supplementation, whereas fabI deletion mutants make only traces of fatty acids and are unsaturated fatty acid auxotrophs. IMPORTANCE: The finding that exogenous fatty acids support growth of E. faecalis strains defective in fatty acid synthesis indicates that inhibitors of fatty acid synthesis are ineffective in countering E. faecalis infections because host serum fatty acids support growth of the bacterium.