He helped popularize the idea that some diseases not previously thought to have a bacterial cause were actually infections, which aroused much controversy when it was first suggested. (2008完型)

难句分析

主句

He helped popularize the idea

主语    谓语                    宾语

同位语从句

(the idea) that some diseases not previously thought to have a bacterial cause 

从属连词                主语          后置定语 

were actually infections

系动词          表语

定语从句

(the idea) which aroused much controversy

从属连词                    谓语      宾语

状语从句

when it was first suggested.

从属连词 主语  谓语

本句是一个多重复合句。主句为He helped popularize the idea，意为“他宣扬这样一种观点。”that some diseases...infections 是同位语从句解释说明the idea，其中，not previously thought to have a bacterial cause 是过去分词短语做后置定语，修饰diseases，意为“之前没有被认为是细菌病源的一些疾病”；which aroused much controversy是定语从句，修饰 the idea；when it was first suggested是时间状语从句，修饰which引导的定从，理解时需要放在定从之前翻译，意为“当这种想法首次提出时，就引起很多争议。”

参考译文

他宣扬这样一种观点，即：之前没有被认为是细菌病源的一些疾病实际上是传染病，当这种想法首次提出时，就引起很多争议。