Lactobacillus plantarum strain 4B2, which exhibits a strong autoaggregating phenotype, receives the broad-hostrange plasmid pAMPl with conjugation efficiencies as high as transconjugants per donor using solid matings; broth matings also occur, but at low transfer frequencies. Filter-sterilized spent supernatant of this strain contains a 32 kDa protein that promotes aggregation, and consequently a high frequency of conjugation, in lactic acid bacteria containing a-l,2-glucose-substituted lipoteichoic or teichoic acids. It appears, therefore, that the substituted lipoteichoic or teichoic acids act as receptors for the aggregation-promoting protein.

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A method to obtain gene transfer in lactic acid bacteria is described. When Streptococcus lactis SH4174 and Lactobacillus reuteri DSM20016 protoplasts undergo fusion by exposure to polyethylene glycol, plasmid pAMβ1 and trehalose‐fermenting ability are transferred into L. reuteri.

Lactobacillus helveticus ATCC 15009 (wildtype) membrane preparations hydrolyzed Mg 2+ -ATP as a function of K + concentration (2-200 mM). Mg 2+ -ATP hydrolysis by L. helveticus membranes was strongly inhibited in the absence of exogenous K + , while it amounted to 6 nmol ATP hydrolyzed min -1 (mg membrane protein) -1 at 50 mM KCl (saturating conditions) and pH 7.2. The K + -dependent ATPase of L. helveticus displayed a relatively high affinity for potassium ions (K m = 800 µM) and was not affected by pretreatment of membranes with N,N'-dicyclohexylcarbodiimide. Membrane preparations were subjected to hypotonic shock to obtain a maximum yield of open profiles. The formation of a maximum level of enzyme-phosphate complex with a molecular mass of approximately 82 kDa was induced upon treatment of L. helveticus membrane preparations with low concentrations of [γ-32 P]ATP in the presence of K + and La 3+ ions and was visualized by acidic SDS-PAGE. It was concluded that L. helveticus membranes contain an inwardly directed K + pump whose presence is discussed in terms of its putative role in cytoplasmic pH regulation.