The Feeding Preference Of Soil Bacteria-feeding Nematodes For Bacteria And Its Physiological And Biochemical Mechanisms

Nematode is one of the main functions of soil animals.It is also most abundant functional group and most widely distributed with 7.6×105-9.2×106/m2 in soil.Since soil food environment favors the growth and development of bacterial-feeding nematodes,the importance of bacterial-feeding nematodes becomes more prominent.Selective feeding is a common phenomenon in animals.Feeding preference of bacterial-feeding nematodes not only changes the microbial quantity,activity and community structure,but also directly affect the survival of Caenorhabditis elegans adapt ability and health.In our experiment,the experiment was set up with Caenorhabditis elegans,Acrobeloides sp.,Mesorhabditis sp.and five bacteria(B.amyloliquefaciens,Variovorax sp.,B.megaterium,P.fluorescens,E.coli)as material.We studied the preference of neamtodes towards live bacteria,killed bacteria and bacterial suspension of five bacteria,and we also studied the preference of nematodes towards different density of bacteria.Feeding-preference was set on nematode growth plate,and the number of nematodes in dots marked on the plates was counted in 1,2,4,8,12,24 h after the nematodes were innocubated.We measured the nutrient content of the five bacteria including carbonhydrate,protein,size,moisture,volatile organic compounds.We studied the mechanisms of feeding preference of the nematodes,following is the main results:We isolated two bacterial-feeding nematodes and one bacteria from the fluvo-aquic soil.The two nematode were Acrobeloides sp.and Mesorhabditis sp.,the bacteria was identified as P.fluorescens.Bacterial-feeding nematodes demonstrated preference towards different bacteria,and nematodes preferred P.fluorescens,but disliked B.amyloliquefaciens and B.megaterium.Compared to G+,bacterial-feeding nematodes preferred G-.The preference of bacterial-nematodes towards live bacteria,killed bacteria and bacterial suspension demonstrated that,the preference of C.elegans towards live bacteria and killed bacteria was not consistent.C.elegans did not show preference for bacterial suspension.The feeding behavior of nematodes for live bacteria demonstrated that the trend of the feeding preference of Acrobeloides sp.for live bacteria and killed bacteria was consistent,but Acrobeloides sp.did not show preference for bacterial suspension.In contrast,the trend of the feeding preference of Mesorhabditis sp.for live bacteria and killed bacteria was not consistent,Mesorhabditis sp.did show preference for bacterial suspension,and the preference order is consistent with the live bacteria.By studying the preferences of bacteria-feeding nematodes for different concentrations of bacteria,we found that,bacteria-feeding nematodes preferred high concentrations of bacteria,and gathered on a high concentration of bacteria.We measured the size,moisture carbonhydrate and protein,the result demonsrated that the preference of bacterial-feeding nematodes for different bacteria was not correlated with carbonhydrate and protein,but correlated with size and moisture.Bacterial-feeding nematodes preferred small bacteria and bacteria with high moisture.By measuring fatty acid and volatile organic compounds of bacteria,we found that the bacteria nematodes preferred were closed in composition,the bacteria nematodes did not preferred are closed in composition.The mechanisms of the preference of bacterial-feeding nematodes needs feather study.