1-Aminocyclopropane-1-carboxylate Deaminase-Producing Bacteria Improve The Adaptability To High Ammonia And High Temperature Of Pleurotus Ostreatus

Pleurotus ostreatus,also known as oyster mushroom,is one of the main cultivated varieties of edible fungi in my country and the world.In recent years,the cultivation of oyster mushroom by using compost substrate has become more and more popular.However,the compost contains relatively high concentrations of ammonia and water-soluble organic carbon.High concentrations of ammonia have toxic effects on oyster mushrooms.The high substrate temperature caused by the high concentration of watersoluble organic carbon also has an inhibitory effect on the oyster mushroom during the mushroom growth period(the substrate temperature is about 10°C higher than the ambient temperature).It is not clear what effect of the high ammonia and high temperature on oyster mushrooms and how to adapt to the high ammonia and high temperature by oyster mushrooms.This work explores the questions.Below are the main research results.(1)The effects of high ammonia and high temperature on the mycelial growth of P.ostreatus were determined.In the PDA plates,the optimum ammonia concentration for the growth of P.ostreatus Heikang 650 and NY-2 was 0.10%-0.20%,and the upper limit was 0.75%.The optimum ammonia concentration and upper limit concentration of Heiping17-1 were both 0.75%.In the sterilized compost,the optimum ammonia concentration for mycelial growth of the three strains was 0.08%-0.25%,and the growth upper limit concentration was 0.25%.In the PDA plates,all three strains showed that the effect of ammonia on mycelial growth was higher than that of temperature in the range of 25-32℃,whereas the effect of temperature was higher than that of ammonia in the range of 32-35℃.The ammonia tolerance of 39 commonly used cultivars was analyzed.The mycelial growth rates of all the cultivars in the plates containing 0.5% NH4 Cl were not higher than that in the plates without NH4 Cl.(2)The effect of ethylene on the mycelial growth of P.ostreatus and the ethylene synthesis pathway of P.ostreatus were analyzed.When Heikang 650 was cultivated in the sterilized compost,ethylene production could be detected,and the ethylene synthesis amount under cultivation at 32 ℃ was significantly higher than that at 25 ℃.Adding ethylene inhibitor 1-MCP to the plates can increase the growth rate of mycelia under high temperature conditions.One 1-aminocyclopropane-1-carboxylic acid(ACC)oxidase(ACO)gene was cloned from the total RNA of Heikang 650.The gene expressed in Pichia pastoris can catalyze the synthesis of ethylene from ACC.It is shown that P.ostreatus had the ACC pathway for ethylene synthesis similar to plants.The P.ostreatus ACO belonged to a novel ACO type by phylogenetic analysis together with ACO proteins from fungi and plants.(3)The growth-promoting effect of ACC deaminase(Acd S)-producing bacteria on P.ostreatus was determined.Abundant Acd S-producing bacteria were detected in the compost.The typical Acd S-producing bacterium Pseudomonas sp.UW4 could colonize the surface of P.ostreatus mycelia,and reduced the ethylene synthesis of P.ostreatus mycelia and promote the mycelial growth under high ammonia and high temperature conditions.Furthermore,the bacterium also induced the formation of primordium and increased the yield of mushrooms.In conclusion,the mechanism of P.ostreatus adapting to high ammonia and high temperature in compost may be that the high ammonia and high temperature of compost had inhibitory effect on P.ostreatus and induced the synthesis of ethylene.The abundant Acd Sproducing bacteria in the compost could reduce the ethylene synthesis of P.ostreatus,relieve the inhibitory effect of ethylene on P.ostreatus,promote the growth of P.ostreatus mycelia,and increase the yield of mushrooms.