| Galactomyces is a typical filamentous fungus in activated sludge fungus micelles,and it is one of the dominant filamentous fungi when filamentous fungal sludge swelling occurs.Galactomyces usually undergoes a series of changes such as spore germination,germ tube length,mycelial morphology,and mycelial properties under environmental pressure.The mechanism of filamentous fungus sludge expansion is that the imbalance of the micro-ecological regulation of filamentous fungi and bacterial results in the overproduction and morphological changes of filamentous fungi,which is essentially the result of poor competition between filamentous bacteria and bacterial.This study proposes that the competition between filamentous bacteria and bacterial is based on the scientific hypothesis that intercellular communication occurs.It is assumed that the Galactomyces fungus has the ability to sense the acylhomoserine lactone AHLs,the representative signal molecule of bacterial,and makes it series response similar under environmental stress.In this paper,the intercellular communication between bacteria and filamentous fungi was used as the entry point.The effects of AHLs on the growth and properties of Galactomyces in a pure culture system were discussed,and the related mechanisms were clarified.First,the dominant filamentous fungi were selected from the micelles of the filamentous fungal sludge bulking and identified as Galactomyces.The effects of different kinds of AHLs,C4-HSL,C6-HSL,C10-HSL and C12-HSL on the growth characteristics and surface properties of Galactomyces fungi were systematically investigated.The results showed that C4-HSL,C6-HSL and C10-HSL stimulated fungal growth and morphology changes,the spore germination rate increased by 4-15%,the hyphae length increased by 6-30%,and the intracellular protein content increased by about At 29%,the polysaccharide content increased by about 47-125%.In addition,the specific growth rate of Galactomyces increased by 62%-181%.However,C12-HSL significantly inhibited spore germination and mycelial growth.Spore germination rate was reduced by 10.8%,hyphae length was inhibited by 11-20%,and mycelium growth rate was inhibited by 16%.Secondly,transcriptome data analysis revealed that C12-HSL suppressed Cyr1-cAMP-PKA to inhibit Ste20 and F-atin actin gene expression,thereby suppressing the polar growth of Bnil hyphae,while suppressing CHS1 chitosan Related gene expression inhibits cell wall formation.In addition,C12-HSL inhibits the expression of Golgi apparatus vesicle formation-related genes,inhibits the transport of vesicles to the top of the mycelium,and inhibits the polar extension of the mycelium.C10-HSL participates in the upregulation of microtubule formation-related proteins and plays a major role in the formation and movement of Galactomyces microtubules.At the same time,C10-HSL promotes the biosynthesis of amino acids,lysine and arginine necessary for mycelial growth by promoting the cycle of tricarboxylic acid,promoting the increase of intracellular protein content and promoting tubulin synthesis.In addition,under the action of C10-HSL,the expression levels of enolase and other genes in the glycolysis pathway are up-regulated,and the expression levels of ATP synthase such as NADH dehydrogenase and succinate dehydrogenase in the oxidative phosphorylation metabolic pathway are all up-regulated,thereby promoting the growth of Galactomyces.C10-HSL and C12-HSL have relatively more significant effects on the growth of Galactomyces mycelium and the expression of related genes,and are the key signaling molecules for the development of filamentous fungal sludge bulking.In this paper,we found that AHLs regulate Galactomyces including spore germination,mycelial growth,and mycelium properties.At the gene level,we analyzed the regulation mechanism of AHLs on Galactomyces,and revealed the reason of filamentous fungal sludge occurrence and provide prevention basic theory from the perspective of intercellular communication. |
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