| Dictyostelid cellular slime molds(dictyostelids)is a kind of special eukaryote,its basic structural unit is naked,monocyte and haploid slime.As an important soil microorganism,it mainly grows in the soil and litter of farmland and forest,where they feeds upon bacteria and other microorganisms,and sometimes grows on animal feces.Because of its short and easily repeat life cycle,also easily separated and completed the observation of the whole life cycle in the laboratory,it becomes an ideal experimental materials in the fields of cytology,genetics,molecular biology,etc.Although domestic and foreign scholars have conducted taxonomic studies on some areas of dictyostelids,there are still many areas where the resources of dictyostelids have not been explored.There is a difference in the preference of the dictyostelids for different bacteria.However,there is little research on which bacteria in the living environment are related to which dictyostelids or prey.Therefore,it is of great significance to explore how dictyostelids chooses and adapt to bacteria in the soil environment to clarify the nature,distribution rules and its coevolutionary relationship with bacteria.In this study,by means of the combination of traditional separation technology and molecular biology technology,we classified and studied the dictyostelids from 14 soil samples which collected from Sakhalin Island,Ussurisk and Vladivostok in the Russina Far East.In addition,soil bacteria were isolated and cultured under four different forest types which including broad-leaved forest,coniferous forest,coniferous and broad-leaved mixed forest and birch forest in Changbai Mountain.Based on 16 S r DNA sequence to carry out the genus level classification status of bacteria.The bacteria in different genera separately and in two mixtures as nutrients to feed dictyostelids yielded from soil samples of the same forest type as those bacteria.At the same time,using Escherichia coli which commonly used in the laboratory as the positive control,sterile water as the negative control.The 16 S amplicons of three important stages of the life cycle(Aggregation,Pseudoplassmodia,Sorocarps)of 3 strains of dictyostelids(MR308,MR310,MR334)were sequenced.The main results are as follows:1.We got 10 strains which belonging to two orders,three families,four genera and seven species.Among them,there are 1 new species(Heterostelium multibrachiatum sp.nov.),4 new Russian records(Cavenderia fasciculata,H.tenuissimum,Dictyostelium longosporum and Polysphondylium patagonicum)and two common species(C.aureostipes and P.violaceum).Three strains were isolated from the soil samples at relatively low altitude(-10 m to 17.7 m),and seven strains were isolated from the soil samples at relatively high altitude(52 m to 184.4 m).The relatively low altitude may not be suitable for the growth of dictyostelids.Except that the new species H.multibrachiatum was isolated from near neutral and strong acid soils,the other six species were isolated from neutral and weak acid soils.Therefore,dictyostelids may be more suitable for survival in near neutral soil.In this study,three species have been reported in the same latitude(P.patagonicum,C.fasciculata and C.aureostripes),and P.patagonicum is the second report in the world.One new species and two new Russian records were obtained in the investigation of dictyostelids resources in Sakhalin Island in the north of the Pacific Ocean.This is the fifth report to date,which provides new research progress for the distribution of dictyostelids in island habitat.2.We have got 111 strains of bacteria belonging to 9 genera which included Bacillus,Pseudomonas,Serratia,Paenibacillus,Microbacterium,Staphylococcus,Stenotrophomonas,Lysinibacillus and Rhodococcus.There was a significant difference on the growth of dictyostelids under the effection of different nutrition types.In the soil environment of 4 types forest in Changbai Mountain,the common isolates of wild bacteria names Bacillus and Serratia,whether as separate nutrition or mixed with other bacteria The growth of dictyostelids is in the dominant level,and it is better than E.coli,which is used in the conventional culture of stipitae.It is the most suitable nutrition for dictyostelids in the forest soil of Changbai Mountain.It provides the basis for obtaining the kinds of bacteria suitable for the growth of dictyostelids.3.There were 234,233 and 237 OTUs in dictyotelids(MR308,MR310,MR334).The species of symbiotic bacteria carried from 3 dictyostelids are different,and the composition of symbiotic bacteria in the 3 stages of the life cycle are different,but the dominant phylum is Proteobacteria,and the dominant genus is Pseudomonas.In addition to food,dictyostelids could carry many kinds of bacteria in different stages of its life cycle,and most of them come from its growing environment soil. |
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