There is a specific UCSC genome browser available for microbes (http://microbes.ucsc.edu/cgi-bin/hgTables?org=Sulfolobus+spindle-shaped+virus+4&db=sulfSpin_VIRUS_4&hgsid=1157632&hgta_doMainPage=1). In the above link, you can find the table browser for Viruses where you can download the GTF file or other formats.