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Phenotypes were compared in two different classes of mutants with defects in murein-lipoprotein (lkyD mutants of Salmonella typhimurium and an lpo mutant of Escherichia coli). Both mutations are associated with the same triad of phenotypic abnormalities, consisting of defective formation of the division septum, leakage of periplasmic proteins during growth, and increased sensitivity to several unrelated external toxic agents. The abnormality in septum formation consists of a defect in invagination of the outer membrane during formation of the nascent septum. The results suggest that formation of the murein-lipoprotein link plays an important role in differentiation of the division septum and perhaps also in maintaining the normal barrier function of the outer membrane.

Small, acid-soluble spore proteins SASP-alpha, SASP-beta, and SASP-gamma as well as a SASP-beta-lacZ gene fusion product were found only within the forespore compartment of sporulating Bacillus subtilis cells by using immunoelectron microscopy. The alpha/beta-type SASP were associated almost exclusively with the forespore nucleoid, while SASP-gamma was somewhat excluded from the nucleoid. These different locations of alpha/beta-type and gamma-type small, acid-soluble spore proteins within the forespore are consistent with the different roles for these two types of proteins in spore resistance to UV light.

Ferritin-conjugated specific antibodies have been used to localize beta-galactosidase and both the monomer and active dimer of alkaline phosphatase in frozen thin sections of cells of Escherichia coli O8 strain F515. The even distribution of the ferritin marker throughout cells that had been induced for beta-galactosidase synthesis, frozen, sectioned, and exposed to ferritin-anti-beta-galactosidase conjugate showed that this enzyme was present throughout the cytoplasm of these cells. Frozen thin sections of cells that had been derepressed for the synthesis of alkaline phosphatase were exposed to both ferritin-anti-alkaline phosphatase monomer and ferritin-anti-alkaline phosphatase dimer conjugates, and the ferritin markers showed a peripheral distribution of both the monomer and the dimer of this enzyme. This indicates that alkaline phosphatase is present only in the peripheral regions of the cell and argues against the existence of a cytoplasmic pool of inactive monomers of this enzyme. This peripheral location of both the monomers and dimers of alkaline phosphatase supports the developing concensus that this enzyme is, like other wall-associated enzymes, synthesized in association with the cytoplasmic membrane and vectorially transported to the periplasmic area, where it assumes its tertiary and quaternary structure and acquires its enzymatic activity.