Microblogs are increasingly used as communication channels for organisations and their related communities. In this work, we are interested in the effect of community on the resulting microblog language use. We analyse content from Twitter, examining tweets relating to two government organisations—one conducting scientific research, the other providing social services. We find that the two different communities have significant differences in style and language use, observing marked differences in formality and tone as measured by properties such as pronominal usage, orthographic convention, and use of Twitter features. We posit that these differences arise due to underlying differences in the communication goals of the two user groups. Tools working with Twitter, to extract and represent information, may therefore need different approaches in different domains.