Disclosed is a printing apparatus that can prevent the occurrence of a transport error and prevent useless printing even when the sheet size of the actually fed sheet is different from the sheet size specified in the printing setting. In particular, methods and compositions for selecting bacterial strains which produce a desired compound are provided. The conductive outer shell includes sidewalls depending from the sides of a face having a plurality of tip seats for receiving a plurality of pipette tips. The composition preferably comprises aluminum chloride, ferric sulfate, regenerated oxidized cellulose, aluminum ammonium sulfate, absorbable gelatin and a solvent. If a particular sub-system fails a test, the cause of failure can be isolated and removed, where possible, and the modified sub-system can be retested.