Bloodhound bees to take the stingout of terrorism
British bees are vying with American wasps to play a role as ultra-sensitive odour detectors, with applications that include sniffing out explosives, diagnosing disease and monitoring food quality.
ADVERTISEMENT
The insects are as sensitive as bloodhounds but can be "trained" far more quickly than dogs to recognise specific molecules.
Scientists have known for decades that insects have amazing olfactory powers, detecting molecules in the air at concentrations below one part per trillion (million million) but they have only recently found ways to exploit that ability.
In the UK a company called Inscentinel, based at Rothamsted Research in Hertfordshire, has been working for four years to harness honey bees for trace vapour detection.
In the US, researchers at the University of Georgia are using parasitic wasps in a similar way.
Because free-flying insects are hard to control, both research teams have developed technology for holding them in portable sensing units. Computer-based image analysis then shows, on the basis of their behaviour, whether the bees or wasps can smell the targetmolecules.
Both types of insect can be trained within a few minutes to recognise a particular molecule, using Pavlovian conditioning. The bees or wasps are fed sugar solution at the same time as they smell the chemical in question - which might, for example, be a man-made explosive or a natural compound produced by decomposing food.
The most obvious difference between the two approaches is that the Georgia wasps fly around inside their Wasp Hound container; a fan draws in air through a pinhole at one end and, if the target molecule is present, the insects crowd around the hole.
Inscentinel's bees, in contrast, are literally strapped into tiny harnesses. Each Inscentinel detection unit contains a "cassette" with three bees and a camera focusing on the insects' heads. In the presence of the odour for which they have been trained, the bees stick out their long proboscis or tongue. Rachael Carson,the company's general manager, says the insects typically spend two days inside the cassette and are then unstrapped to returnto their hive - showingno signs of distress.
The main funding for both systems so far has come from government defence and security organisations. "I think the first commercial applications will be in ???-security screening," says Dr Carson. "We have done field trials with explosives hidden in cars and we are about to start a trial looking for explosives in air cargoshipments."
Inscentinel - which is funded by Oxford Technology Venture Capital Trusts - is also working on medical applications, training the bees to sniff out "indicator" molecules produced by particular bacteria and tumours. One project with the London School of Hygiene and Tropical Medicine aims to diagnose tuberculosis, another with Amersham Hospital focuses on bladder cancer.
Dr Carson says there are also promising applications in the food and drink industry - for example, to detect deterioration in freshly squeezed orange juice.
The Georgia team is also working on non-security applications for its Wasp Hound, such as detecting leaks in chemical pipelines and natural toxins produced by fungi in nuts andother foods.
No head-to-head comparisons between the systems have yet been published. But each team sees sniffer dogs and "electronic nose" instruments as the main competition. "We are 100 times more sensitive than electronic nose technology," says Glen Rains of the University of Georgia, "and dogs can take six months and cost $15,000 (￡8,500) to train."
If sniffer insects win a niche in the chemical detection market, theremay be room for both bees and wasps.
昆虫鼻子的商用价值
英
国蜜蜂正与美国黄蜂争夺超灵敏气味探测器的美名，应用包括嗅出炸药、诊断疾病和监测食品质量。
昆虫和侦探犬一样敏感，但通过“训练”，昆虫识别特殊分子的速度比猎犬快许多。
几十年前，科学家就已知道昆虫的嗅觉能力惊人，在空气密度低于一万亿分之一时可探测到分子，但他们直到最近才找到充分发挥这种能力的方法。
Inscentinel是一家总部位于赫特福德郡洛桑研究所(Rothamsted Research)的英国公司。在过去的四年中，该公司一直致力于利用蜜蜂追踪蒸气探测。
美国佐治亚大学(University of Georgia)的研究人员正以类似的方式利用寄生黄蜂。
由于自由飞行的昆虫难以控制，这两支研究团队已开发了将它们置于手提传感器内的技术。这样，基于计算机的图像分析将根据蜜蜂或黄蜂的行为证明它们能否闻到目标分子。
这两类昆虫经过训练可在几秒内，利用巴甫洛夫条件反射作用识别出特殊分子。在蜜蜂或黄蜂去闻被怀疑的化学制品的同时，向它们喂食糖水。举例来说，这种化学制品可能是人造炸弹或腐烂食物产生的自然混合物。
这两种方法最明显的区别在于佐治亚大学的黄蜂在“黄蜂猎犬”容器内飞来飞去；一个风扇通过一端的针孔吸入空气，如果目标分子存在，那么昆虫就会聚集在针孔周围。
相比之下，Insentinel的蜜蜂实际上是被捆在极小的挽具内。每一个Insentinel探测器内有一盘装着3只蜜蜂的“盒式磁带”和一部瞄准昆虫头部的照相机。当嗅到训练时闻过的气味，蜜蜂就会伸出长长的鼻子或舌头。Insentinel的总经理雷切尔?卡森(Rachel Carson)说，昆虫一般会在盒式磁带内待两天，然后解开捆绑，回到它们的蜂箱中――毫无痛苦迹象。
迄今为止，这两种研究方法的资助主要来自政府国防和安全组织。“我认为，首次商业应用将出现在安全检查中，”卡森博士说，“我们已对藏在车上的炸药进行了实地试验，并将在航空货运中开始寻找炸药的实验。”
此外，受到牛津技术创业投资信托(Oxford Technology Venture Capital Trusts)资助的Inscentinel还致力于医学应用的研究，训练蜜蜂嗅出特殊细菌和肿瘤产生的“指示剂”分子的能力。与伦敦卫生和热带医学院(London School of Hygiene and Tropical Medicine)的合作项目旨在诊断肺结核，另一个项目则是与阿默舍姆医院(Amersham Hospital)合作研究膀胱癌。
卡森博士说，应用于食品和饮料领域的前景也很光明。例如，在鲜榨橙汁中发现变质现象。
佐治亚大学的研究队伍也正致力于“黄蜂猎犬”的非安全应用的研究，例如，探测化学管道中的裂缝，以及由坚果和其它食物中的真菌生成的自然毒素。
两种方法直接的比较结果尚未公布，但它们都将嗅探犬和“电子鼻”仪器视为主要的竞争对手。“我们的方法比电子鼻技术敏感100倍，”来自佐治亚大学的格伦?雷恩斯(Glen Rains)说，“而且，要训练一只狗需要6个月，花费1.5万美元。”
如果“嗅探虫”能在化学探测市场赢得一席之地，那么蜜蜂和黄蜂将前途无量。
