Joint Research with Masis, Inc.
In cooperation with Masis, Inc., we are pursuing the establishment and commercialization of the methods to detect toxic and pathogenic substances contained in farm products, foods, and environment by using silkworm as a tester.
Purpose of Research
The food-poisoning incident by the imported foods polluted with agricultural chemicals is still fresh in our memory. Agricultural products, foods, and environment are polluted with toxic substances such as arsenic and organic mercury and similar cases have often occurred. In most of these cases, toxic substances were detected and identified after people become sick, which is too late for consumers. Physicochemical techniques (HPLC method and ELISA method) are employed to identify toxic substances. For consumers, the answer for “Is a poison contained?” is much more important than that for “What kind of poison is contained?”. There is no technique to detect and identify all kinds of toxic substances. Lethality tests using mammals such as mice are high-cost and evoke ethical issue. Thus, it is necessary to develop methods to detect any kind of toxic substances cheaply and quickly.
Content of Research
As shown in Table 1, we have discovered that lethal doses per body weight (LD50) of many chemicals for silkworms and mammals were similar each other. Bacteria pathogenic for human also kills silkworms and nonpathogenic bacteria does not. We also found that bacteria isolated from oil well water with higher ability to kill silkworms potently kill mice. These results demonstrated that silkworm was useful as a tester to detect toxic substances and pathogenic bacteria contained in foods. At present, we study sensitivity of silkworm system to detect various toxic substances and pathogenic bacteria in several kinds of materials and pursue the commercialization of this system in cooperation with Masis, Inc.
Table1. Comparison of lethal doses of the toxic substances between silkworm and mammal
| toxic substance | LD50 (μg/g・animal)a |
|
| silkworm | mammal(mouse/rat) | |
| ethanol | 9500 | 10000 |
| methanol | 2100 | 2130 |
| DMSO | 33000 | 11530 |
| DMF | 16000 | 2800 |
| phenol | 310～3100 | 310 |
| cresol | 0.63 | 2 |
| sodium chloride | 9100 | 4000 |
| ferric sulfate | 220 | 1500 |
| copper sulfate | 310 | 960 |
| sodium azide | 380 | 45 |
| pottasium cyanide | 115 | 8.7 |
aAn LD50 represents the dose required to kill 50 percent of a population of test animals .
Table2. Pathogenicity of bacteria isolated from the oil well water in silkworm and mouse
| strain a | ability to kill silkworms b | ability to kill mice c |
| #1 | + | – |
| #2 | + | – |
| #3 | + | – |
| #5 | + | ++ |
| #6 | ++ | +++ |
| #7 | +++ | + |
| #8d | ++++ | +++ |
| #10 | + | - |
| #13 | + | - |
| Staphylococcus aureus | + | +++ |
| Escherichia coli | - | – |
a Decided by the sequence of rRNA gene
b Minimum bacterial density which killed silkworms [dilutions: 1/1 (+), 1/10 (++), 1/100 (+++), 1/1000 (++++) ].
c Number of survivors when 1/1 dilution of bacterial cell suspension was injected to mice; [3/3 (-), 2/3 (+), 1/3 (++), 0/3 (+++)].
d Bacterium recently discovered from the abalone. Its pathogenicity was not investigated.
Figure 1. Some kinds of bacteria isolated from the oil well water and were potently pathogenic killed both silkworms and mice
Please refer to the following website about detailed information of this joint research.
