Effects of low temperature on the growth,metabolism,and quorum sensing of heterotrophic nitrifying bacteria Acinetobacter sp.
To further explore the mechanism of nitrogen transformation and quorum sensing system of HN-AD bacteria under low temperature,there were at least three AHLs signaling molecules,including C6-,C8-,and C10-HSL produced by the HN-AD bacterium JQ1004 based on the analysis of GC-MS.The concentration of AHLs showed a significant density dependence and continuously accumulated with the increase of biomass.When the temperature decreased from the optimal 30℃to 10℃,C6-and C8-HSL showed a continuous decreasing trend due to the decrease of cell concentration,while the concentration of C10-HSL increased first and then decreased,reaching a maximum value of 10.89nmol/L at 20℃,indicating that C10-HSL played a crucial role in the bacterial adaptation to low-temperature environments.Further study found that adding 10nmol/L C10-HSL at low temperature could significantly shorten the bacterial lag period and improved the nitrogen removal rate.The addition of C10-HSL at 20℃and 10℃increased the expression of amoA by 35%and 22%,respectively,while the expression of napA increased by 14%and 9.4%.C10-HSL enhanced the ability of quorum sensing of strains by increasing the receptor protein activity regulated by luxR.Adding C10-HSL at low temperature could promote extracellular protein secretion,reduce polysaccharide content,improve biofilm activity,and strengthen its adaptability to harsh low-temperature environments.
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