Sphingopyxis terrae, and Sphingopyxis macrogoltabida strains 103 and 203, can degrade polyethylene glycols (PEGs). They differ in the following respects: (i) different substrate specificities (chain length) of assimilable PEG, (ii) PEG-inducible or constitutive PEG-degradative proteins, and (iii) symbiotic or axenic degradation of PEG. S. terrae was able to incorporate PEG 6000, but strain 103 ...