Reports have demonstrated increased production in phaZ-knockout mutants of P. putida strain U [1] and P. putida KT2442 [3], while others have found that neither a mutant of P. putida GPo1 lacking part of the phaZ gene [14] nor transposon-disrupted phaZ minus mutants of P. resinovorans [34] showed any substantial difference in PHA accumulation under conditions favorable to PHA synthesis.