Isolation, Culture And Identification Of Bdellovibrio Bacteria And Its Biological Characteristics

Bdellovibrio is a small and highly active gram negative bacterium,which is smaller in size than most bacteria and it can pass rapidly through a bacterial filterless.Bdellovibrio has acquired its own nutrients by attacking other gram negative bacteria and acts like bacteriophages.Bdellovibrio is ubiquitous in nature and can be separated from different sources,including plant roots,fresh water,soil and animal gastrointestinal tract.The samples in this experiment were collected from hoggery and Escherichia coli was used as host strain to enrich and separate the isolates.The isolates were stained with gram,and it would be Gram-negative bacteria if that was red observed by microscopy.The size of the Brevibacterium was 0.4~0.6?m×0.8~1.0?m in accordance with the size of the Bacteroides.The morphology of E.coli changed dramatically and an end of the cell expanded after staining on attacked E.coli.Isolated Bdellovibrio was tested for PCR and the results showed that the two pairs of primers were successfully ran out of specific bands and the fragment size were basically match.The PCR product was sent for sequencing and the sequence was 574 bp.The fragment size of sequence were basically coincide with the target fragment.The biological characteristics of Bdellovibrio in this experiment was studied,which includied the optimization experiments of the culture medium,the host bacteria the cleavage ability test and the simple preservation of the Bacteroides.The LB medium and the broth(NB)liquid medium were optimized by observing the growth of expansion spots.LB medium was more suitable for the growth of Vibrio vulgaris than liquid broth.In the experiment of screening the concentration of host bacteria,the expansion spot was observed after incubation with different concentrations of the host.The results showed that the activity of Bdellovibrio was stronger under the condition of high concentration of host bacteria.It indicatied that the higher concentration is more suitable for the Bdellovibrio's growth.Detection of the cleavage ability of Bdellovibrio on three strains:change the host bacteria into Pasteurella,Salmonella and Staphylococcus aureus to observed whether they would in the shape of the expansion spots or host bacteria would expand,agents were Gram stained with swells,besides,taking count for these three kinds of bacteria.The result showed that Bdellovibrio has the ability to crack bacteria on these three kinds of bacteria.It has a certain degree of aggression towards the bacteria in the solid culture,while it can not stop the proliferation of the host bacteria in the liquid medium.The orthogonal experiments were carried out with temperature,glycerol concentration and host concentration as the factors to examine its stability.The temperature were set at 25?,4?,-20?;The concentration of glycerol were set at zero,15%,20%;The concentration of host bacteria were set at 10~3cfu/mL,10~5 cfu/mL,10~7 cfu/mL.15%glycerol can makes Bacteroides more stable.Bdellovibrio survived more than 180 days,in comparison to low temperature and higher concentrations of host bacteria is more conducive to the preservation of Bdellovibrio.