请问这句英语中的某段是什么短语?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 suggesed.这段话中的“ some diseases not previously thought to have a bacterial cause” 属于什么类型的短语?

请问这句英语中的某段是什么短语?
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 suggesed.
这段话中的“ some diseases not previously thought to have a bacterial cause” 属于什么类型的短语?