| Mushrooms are favored by consumers for their nutrition,great taste,and healthcare function.There are dry mushrooms and fresh mushrooms.Since cold-chain transportation and sales are not applied to all the mushrooms,fresh mushrooms are rotting gradually at room temperature for the propagation of exogenous bacteria.In this study,a variety of fresh mushrooms such as Lentiluna edodes were sampled as materials.In order to explore the diversity,quantity and the dynamic change of exogenous bacteria on the fruiting-body of mushrooms.both plate culturing and 16 S rDNA high-throughput sequencing were used in this study.On this basis,a rapid method for detecting the dominant bacteria of Flammulina velutipes was developed.The main results of the research were as follows:1.Both plate culturing and 16 S rDNA high-throughput sequencing were used to detect the diversity and quantity of exogenous bacteria on 9 species of fresh mushrooms.The results of plating method showed that the predominant species of exogenous bacteria was Ewingella americana,followed by Lactococcus lactis subsp.lactis.16 S rDNA high-throughput sequencing method showed that fresh mushrooms such as Agaricus bisporus,Agrocybe cylindracea,Hericium erinaceus,Hypsizygus marmoreus and Pleurotus ostreatus had the highest abundance of Pseudomonas;Auricularia auricula,F.velutipes,L.edodes and Pleurotus eryngii,had the highest abundance of Sphingomons,Lactococcus,Burkholderia and Erwinia,respectively.The results of diversity analysis showed that the most abundant species of exogenous bacteria were propagated on the fruiting body of A.auricula,while the lowest bacteria abundance was detected on that of P.eryngii.The exogenous bacteria communities of L.edodes,P.eryngii and A.cylindracea were significantly different from the other six mushrooms.2.The quantity and species diversity of the exogenous bacteria on the fruiting body of F.velutipes,P.eryngii and H.marmoreus were explored during the shelf life of 1-5 days.The quantity of exogenous bacteria in shelf life increased significantly from day1 to day5,by 35 fold(H.marmoreu),418 fold(F.velutipes)and 4117 fold(P.eryngii).The results of plate culturing method showed that the dominant bacteria were E.americana and Obesumbacterium proteus in the shelf life of F.velutipes,Raoultella ornithinolytica and Serratia rubidaea were in H.marmoreus,and E.americana and P.beijingensis were in P.eryngii.The results of 16 S rDNA high-throughput sequencing method showed that the abundance of exogenous bacterial species of F.velutipes was lower than that of H.marmoreus and P.eryngii.There was a large quantity of Pseudomonas spp.and Lactococcus spp.on the surface of the three kinds of mushrooms.The abundance of Pseudomonas spp.was highest among all the exogenous bacteria on H.marmoreus and P.eryngii,and it increased as the shelf life became longer.The abundance of Lactococcus spp.was highest of F.velutipes,and it showed a downward trend as shelf life prolonged.Between these two methods,16 S rDNA high throughput sequencing method had a more comprehensive detection of species,and performed quantitative analysis on the abundance change of bacteria.3.A rapid method for detecting Lactococcus by using LAMP technique was established.Lactococcus as the advantage bacterium of F.velutipes was used as the testing bacteria,and a set of primers for genomic conserved sequences were designed.The results showed that the specificity of the primer rpoA289 was reasonably specific;the testing sensitivity of genomic DNA of Lactococcus was as low as 0.9pg/?l;the sensitivity of bacteria suspension was as low as 3.3CFU/ml. |
PDF Full Text Request