| In this paper, a photobacterium strain from frozen pork was got and identificated based on a series of physiological and biochemical detections, spectral measurements, morphology observations, and sequences against three genes named16SrDNA gene, gyrB gene, and luxA gene. Compared with the Bergry’s Manual of Systemaic Bacteriology, the result showed that the isolated luminous bacterium was consistent to the Photobacterium Beijerinck1889,41. Furthermore, this bacterium was identificated to be Photobacterium phosphoreum according to the genetic sequences comparison of the gyrB and luxA. The gyrB Phylogenetic Tree and the luxA Phylogenetic Tree showed the same results as the strain Photobacterium phosphoreum PB-P3.9and the reference strain P. phosphoreum NCIMB1279have the closest genetic relationship. The latter is the symbiont of deep-water fishers (such as Macrouridae and Salmonidae), or lives in the plankton in the middle sea water. Accordingly, Photobacterium phosphoreum PB-P3.9should come from the ocean.Photo-bacteria bioassay is a type of rapid, sensitive, reproducible and cost-effective bacterial assay for the environmental toxicity testing. Therefore, many researchers pay more and more attentions on these studies. However, the species of Photobacterium we can use are limited and three kinds of luminous bacterium are only applicated in our country, which are mainly Photobacterium phosphoreum T3, Vibrio Fischeri, and Vibrio qinghaiensis Q67, respectivily. In this work, Photobacterium phosphoreum PB-P3.9was also utilized to test the environmental toxicity. The same results were found that four types of actual water samples were detected by fresh bacterium fluid and microscopy,respectively. Moreover, two heavy metal compounds were detected via fresh bacterium culture and a good linear relationship was presented. The median effective concentration (EC50) were calculated and had the same results as reported before. Then the bacteria freeze-dried powder was made and the acute toxicity of the two heavy metal compounds (chlorinated mercury and chlorinated cadmium) was tested by the bacteria suspension after rehydration. The toxicity tests showed a good linear relationship. Additionally, the sensitivity of the detection bacteria was significantly improved compare with the fresh bacteria. All in all, it was concluded that the strain Photobacterium phosphoreum PB-P3.9can be used well as the environment toxicity monitor.This paper includes the following researches:1. Isolation and purification of a luminous bacterium from frozen pork. Completed the system certification by physiological and biochemical detection, related gene amplification and sequencing analysis. Finally, the causes of luminescence pork and the source of this strain photobacterium were found.2. Rapid detection analysis on environment toxicity test was performed using the purified bacteria. Four types of actual water samples were determined, based on fresh bacterium fluid detection and microscopy, respectively. Moreover, the acute toxicity of two heavy metal compounds (chlorinated mercury and chlorinated cadmium) were detected by fresh bacterium suspension. An important prospect was well displayed for this photobacterium, based on actual water samples detection and heavy metal compounds toxicity detection analysis.3. The photobacterium freeze-dried powder was produced. Cryoprotective solution and bacteria culture conditions under the freeze-drying procedure were determined. According to luminescence testing, the results showed that the luminescence was stability after rehydration many times and had a good recovery effect. Compared with the fresh bacteria, the detection sensitivity of bacteria was improved significantly in toxicity detection of heavy metal compounds by freeze-dried powder. Additionally, the freeze-dried powder, because of the easy storage and transport, convenient and quick, should have excellent application if it is used to detect and monitor the environment toxicity. |
PDF Full Text Request