At the onset of infection, the virus introduces into the cell its genetic material —RNA or DNA— accompanied in many instances by essential proteins.

Viruses are submicroscopic agents which infect plants, animals and bacteria.

The principal micro organisms involved are all chemoorganotrophs and derive their carbon and energy supply from the metabolism of organic compounds.

A. 代谢物
B. 代谢率
C. 新陈代谢
D. 代谢分子

Of the Gram-positive organisms, aerobic, endospore-forming bacteria of the genus bacillus, some coryneform bacteria (Corynebacter-ium and Brevibacterium) and the filamentous bacteria (actinomycetes) particularly of the genus Streptomyces are well represented.

A. 好氧的
B. 厌氧的
C. 好氧菌
D. 厌氧菌

Gram-negative types include acetic acid bacteria and Xanthomonads(黄单胞杆菌).

A. 革兰氏阴性菌
B. 革兰氏阴性的
C. 革兰氏阳性菌
D. 革兰氏阳性的

The relevant characteristics of these microorganisms are that they should be non-pathogenic, easy to maintain and cheap to grow.

A. 致病菌
B. 非致病菌
C. 病态的
D. 非病态的