Bactoprenol, ATPase and acetate activating enzymes of a vesicular fraction from Lactobacillus casei

Cloning, sequence analysis, and hyperexpression of the genes encoding phosphotransacetylase and acetate kinase from Methanosarcina thermophila

The genes for the acetate-activating enzymes, acetate kinase and phosphotransacetylase (ack and pta), from Methanosarcina thermophila TM-1 were cloned and sequenced. Both genes are present in only one copy per genome, with the pta gene adjacent to and upstream of the ack gene. Consensus archaeal promoter sequences are found upstream of the pta coding region. The pta and ack genes encode predicted polypeptides with molecular masses of 35,198 and 44,482 Da, respectively. A hydropathy plot of the deduced phosphotransacetylase sequence indicates that it is a hydrophobic polypeptides; however, no membrane-spanning domains are evident. Comparison of the amino acid sequences deduced from the M. thermophila and Escherichia coli ack genes indicate similar subunit molecular weights and 44% identity (60% similarity). The comparison also revealed the presence of several conserved arginine, cysteine, and glutamic acid residues. Arginine, cysteine, and glutamic acid residues have previously been implicated at or near the active site of the E. coli acetate kinase. The pta and ack genes were hyperexpressed in E. coli, and the overproduced enzymes were purified to homogeneity with specific activities higher than those of the enzymes previously purified from M. thermophila. The overproduced phosphotransacetylase and acetate kinase migrated at molecular masses of 37,000 and 42,000 Da, respectively. The activity of the acetate kinase is optimal at 65 degrees C and is protected from thermal inactivation by ATP. Diethylpyrocarbonate and phenylglyoxal inhibited acetate kinase activity in a manner consistent with the presence of histidine and arginine residues at or near the active site; however, the thiol-directed reagents 5,5'-dithiobis (2-nitrobenzoic acid) and N-ethylmaleimide were ineffective.

Preparation and regeneration of bacteriophage PL-1 enzyme-induced Lactobacillus casei protoplasts

Lactobacillus casei ATCC 27092 protoplasts were obtained by treatment with a bacteriolytic enzyme, which was produced in the PL-1 phage lysates of this bacterium, at 37 degrees C for 1.5 h in 50 mM Tris hydrochloride buffer (pH 7.2) containing 20% sucrose and 10 mM MgSO4. The protoplasts lacked the cell wall layer but retained the ability to transport L-[3H]glutamine. The frequency of regeneration was about 1%, whereas about 99% of the cells were osmotically sensitive.

Assembly of D-alanyl-lipoteichoic acid in Lactobacillus casei: mutants deficient in the D-alanyl ester content of this amphiphile

D-Alanyl-lipoteichoic acid (D-alanyl-LTA) from Lactobacillus casei ATCC 7469 contains a poly(glycerophosphate) moiety that is acylated with D-alanyl ester residues. The physiological function of these residues is not well understood. Five mutant strains of this organism that are deficient in the esters of this amphiphile were isolated and characterized. When compared with the parent, strains AN-1 and AN-4 incorporated less than 10% of D-[14C]alanine into LTA, whereas AN-2, AN-3, and AN-5 incorporated 50%. The synthesis of D-[14C]alanyl-lipophilic LTA was virtually absent in the first group and was approximately 30% in the second group. The mutant strains synthesized and selected the glycolipid anchor for LTA assembly. In addition, all of the strains synthesized the poly(glycerophosphate) moiety of LTA to the same extent as did the parent or to a greater extent. It was concluded that the membranes from the mutant strains AN-1 and AN-4 are defective for D-alanylation of LTA even though acceptor LTA is present. Mutant strains AN-2 and AN-3 appear to be partially deficient in the amount of the D-alanine-activating enzyme. Aberrant morphology and defective cell separation appear to result from this deficiency in D-alanyl ester content.

Production and Regeneration of Lactobacillus casei Protoplasts

Methods for the production and regeneration of Lactobacillus casei protoplasts are described. Protoplasts of L. casei strains were obtained by treatment with mutanolysin or with mutanolysin and lysozyme together in a protoplast formation buffer containing 0.02 M HEPES ( N -2-hydroxyethylpiperazine- N′ -2-ethanesulfonic acid) (pH 7.0), 1 mM MgCl 2 , 0.5% gelatin, and 0.3 M raffinose. Cells were regenerated on a complex medium supplemented with bovine serum albumin, MgCl 2 , CaCl 2 , gelatin, and raffinose. Lengthy digestion with lytic enzymes inhibited the capacity of protoplasts to regenerate. The optimum conditions of protoplast formation varied from strain to strain. Using predetermined optimal conditions it was possible to prepare protoplasts of several L. casei strains and regenerate them with 10 to 40% efficiency. The methods were applicable to other species of lactobacilli as well.

Mesosomes: membranous bacterial organelles

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Conservation and transformation of energy by bacterial membranes

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