The present invention provides live, attenuated Mycoplasma gallisepticumbacteria that exhibit reduced expressionof a protein identified as MGA0621. In certain embodiments, the attenuatedbacteria may additionally exhibit reduced expressionof one or more proteins selected from the group consisting of pyruvatedehydrogenase, phosphopyruvate hydratase, 2-deoxyribose-5-phosphate aldolase, and ribosomal protein L35, relative to a wild-type M.gallisepticum bacterium. Also provided are vaccines andvaccination methods involving the use of the live, attenuated M. gallisepticumbacteria, and methods for making live attenuated M.gallisepticum bacteria. An exemplary live, attenuated strain of M.gallisepticum is provided, designated MGx+47, which was shownby proteomics analysis to exhibit significantly reduced expression of MGA0621,and was shown to be safe and effective whenadministered as a vaccine against M. gallisepticum infection in chickens.
