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Chemolithoautotrophic Campylobacterota are widespread and predominant in worldwide hydrothermal vents, and they are key players in the turnover of zero-valence sulfur. However, at present, the mechanism of cyclooctasulfur activation and catabolism in Campylobacterota bacteria is not clearly understood. Here, we investigated these processes in a hydrothermal vent isolate named Sulfurovum indicum ST-419. A transcriptome analysis revealed that multiple genes related to biofilm formation were highly expressed during both sulfur oxidation and reduction. Additionally, biofilms containing cells and EPS coated on sulfur particles were observed by SEM, suggesting that biofilm formation may be involved in S0 activation in Sulfurovum species. Meanwhile, several genes encoding the outer membrane proteins of OprD family were also highly expressed, and among them, gene IMZ28_RS00565 exhibited significantly high expressions by 2.53- and 7.63-fold changes under both conditions, respectively, which may play a role in sulfur uptake. However, other mechanisms could be involved in sulfur activation and uptake, as experiments with dialysis bags showed that direct contact between cells and sulfur particles was not mandatory for sulfur reduction activity, whereas cell growth via sulfur oxidation did require direct contact. This indirect reaction could be ascribed to the role of H2S and/or other thiol-containing compounds, such as cysteine and GSH, which could be produced in the culture medium during sulfur reduction. In the periplasm, the sulfur-oxidation-multienzyme complexes soxABXY1Z1 and soxCDY2Z2 are likely responsible for thiosulfate oxidation and S0 oxidation, respectively. In addition, among the four psr gene clusters encoding polysulfide reductases, only psrA3B3C3 was significantly upregulated under the sulfur reduction condition, implying its essential role in sulfur reduction. These results expand our understanding of the interactions of Campylobacterota with the zero-valence sulfur and their adaptability to deep-sea hydrothermal environments. [ABSTRACT FROM AUTHOR]

To investigate the relationship between starch hydrolysis and Monascus pigments (MPs) production, the α-amylase gene (AOamyA) from Aspergillus oryzae was heterologously expressed in Monascus ruber CICC41233, and we obtained a positive transformant named Monascus ruber Amy9. In M. ruber Amy9, the α-amylase activities were 6.65- and 4.26-fold higher at 72 h and 144 h, respectively, than those in the parent strain with the glucose as solo carbon medium. Surprisingly, in the MPs fermentation medium with rice powder as solo material, M. ruber Amy9 completely degraded starch at 48 h, while 43.93 and 7.29 mg/mL starch remained at 48 and 144 h, respectively, in the parent strain. Monascus ruber Amy9 accelerated starch hydrolysis, which enhanced biomass and also increased total MPs by 132% after 144 h. Compared with M. ruber CICC41233, the relative gene expression levels, as determined by a quantitative real-time polymerase chain reaction analysis, of acl2 encoding ATP-citrate lyase subunit 2, pks encoding polyketide synthase, and fasB encoding the fatty acid synthase beta subunit increased by 33.14, 145.18, and 32.15%, respectively, after 144 h in M. ruber Amy9. The up-regulated expression of these key genes in MPs synthesis contributed to the large increase in MPs production. This interesting work provided us with a new idea and a new target for the study of the MPs production. [ABSTRACT FROM AUTHOR]