Symbiosis
48. The twists and turns of fate
Aug 21st 2008 From The Economist print edition

Helicobacter pylori has a reputation for causing ulcers and cancer. Hunting it to extinction, however, may be a mistake

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MOST people feel a twinge of regret at reports that an animal or plant is becoming rare. Should they feel the same pangs for a bacterium? With Helicobacter pylori, so-called because of its twisty-turny shape, and famous for causing stomach ulcers and gastric cancer, the reaction would probably be 'good riddance'. And H. pylori is, indeed, endangered in many parts of the planet. It is fast vanishing from the rich world, thanks to antibiotics and improved hygiene. Yet, as conservationists of larger organisms are quick to remind you, extinctions can have unexpected consequences. And that may prove to be the case with H. pylori.
Martin Blaser, a microbiologist at the New York University School of Medicine, and his team have already linked the bug's disappearance with increased levels of obesity and with the rise of cancer of the oesophagus. Last month they added asthma to the list by publishing a study showing that children who had not been infected by H. pylori were more likely to suffer from the condition than those who had.
It is a mistake, according to Dr Blaser, to think of H. pylori as just another pathogen. He reckons that it is better perceived as a symbiont that is sometimes helpful and sometimes harmful. The evidence suggests that its relatives have been living in mammalian stomachs since the mammals began, some 150m years ago. It, itself, has been around for at least 60,000 years and until about 50 years ago it infected 70-80% of the human population. Now, as a consequence of the routine use of antibiotics for such things as ear infections, only 5% of American children have it. That change, he thinks, is having consequences.

A. 어휘
symbiosis 共生(공생). reputation 명성 ulcer 潰瘍(궤양).
extinction 死滅(사멸), 滅種(멸종).
twinge 激痛(격통). pang 悲痛(비통). twisty-turny 螺旋形(나선형)의 꾸불꾸불한.
gastric cancer 위암. riddance 一掃(일소), 제거. vanish 사라지다.
antibiotics 抗生劑(항생제). hygiene 위생. conservationist 자연보호론 자.
organism 유기체, 생물. consequence 결과. microbiologist 미생물학자.
School of Medicine 醫科大學(의과대학). bug 미생물, 병균, 곤충.
obesity 비만. oesophagous 食道(식도). asthma 천식.
infect 감염되다. condition→asthma. pathogen 병원균. reckon 판단하다.
perceive 감지하다, 지각하다, 이해하다. symbiont [생물] 共生者(공생자).
evidence 증거. relative 친척. mammalian 포유동물의.

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Give and take
Dr Blaser has discovered, for example, that H. pylori helps to regulate stomach-acid levels in a way that is usually helpful to both itself and its host. If the human side of the loop gets too strong, and the stomach becomes too acid, the bug may produce a substance called cag. The intended effect of this, Dr Blaser thinks, is to say 'turn down the acid level'. However, cag also has a side-effect. It is toxic to the stomach lining, and it is this toxicity that provokes the ulcers and cancers for which H. pylori is notorious.
The obvious medical temptationand, indeed, what has happened in practiceis to annihilate the bacterium with antibiotics. That works as an anti-ulcer treatment, but when H. pylori goes its homeostatic effect goes with it, allowing the strength of the stomach acid to rise chronically. This acid has a tendency to spill out of the top of the stomach and into the oesophagus. That has unpleasant consequences. In fact the recent drop in H. pylori infections has almost exactly matched the rise in gastroesophageal reflux disease (which feels like bad heartburn). Over time, the damage the excess acid does to the walls of the oesophagus may cause cancer.

A. 어휘
regulate 통제하다, 규정하다. stomach-acid 胃酸(위산). host 宿主(숙주).
loop 곡선, 고리, 振幅(진폭)이 가장 큰 부분. substance 물질.
intended effect 의도된 효과. side-effect 부작용. toxic 有毒(유독)한, 독성이 있는. stomach lining 胃의 內壁(내벽). toxicity 毒性(독성). provoke 일으키다, 화나게 하다. notorious 악명 높은. obvious 명백한. temptation 유혹.
annihilate 壞滅(괴멸)시키다, 몰살시키다. treatment 치료.
homeostatic 恒常性(항상성)의 [생체내의 균형을 유지하려는 경향].
chronically 만성적으로. spill-spilt-spilt 흘러나오다, 엎지르다. oesophagus 식도.
gastroesophageal 胃(위)-食道(식도)의. reflux 逆流(역류).
gastroesophageal reflux disease 위에서 식도로 위산이 역류하는 병.
heartburn 가슴앓이. excess acid 과잉위산.

B. 구문
- the human side of the loop gets too strong
[인간숙주와 병원균간의 세력균형 곡선에서]숙주 쪽이 너무 우세해지면]
- when H. pylori goes its homeostatic effect goes with it
[헬리코박터균이 사라지면 그것이 유지하고 있던 평형효과도 함께 사라진다].