ABSTRACT

The lipid and fatty acid profiles of eight Helicobacter spp. (H. nemestrinae, H. acinonyx, H. canis, Helicobacter sp. strain CLO-3, ''H. rappini'' [Flexispira rappini], H. pametensis, Helicobacter sp. strain Bird-B, and Helicobacter sp. strain Bird-C) and the fatty acid profiles of five additional species (H. pylori, H. felis, H. muridarum, H. mustelae, and H. fennelliae) were analyzed and compared. A heterologous fatty acid profile was observed among the Helicobacter spp., and on that basis the species could be divided into two groups. Group A had 19-carbon cyclopropane fatty acid (19:0cyc) and tetradecanoic acid (14:0) as the major fatty acids, and group B characteristically lacked the 19:0cyc and had hexadecanoic acid (16:0) and octadecenoic (18:1) acids as the major fatty acids. The species of group A are primarily gastric colonizers, and those of group B are primarily intestinal colonizers. Seven of the eight species studied showed the unusual and characteristic presence of cholesteryl glucosides (CGs), and most of these seven showed a very large amount (9.7 to 27.4% of the weight of total extractable lipid). The types of CGs and their distribution in different species were as follows: cholesteryl-6-O-acyl-␣-D-glucopyranoside (cholesteryl-6-O-tetradecanoyl-␣-D-glucopyranoside in H. nemestrinae and mainly cholesteryl-6-O-dodecanoyl-␣-D-glucopyranoside in ''H. rappini''), cholesteryl-␣-D-glucopyranoside (H. nemestrinae, H. acinonyx, H. canis, Helicobacter sp. strain CLO-3, and ''H. rappini''), and cholesteryl-6-O-phosphatidyl-␣-D-glucopyranoside (H. nemestrinae, H. acinonyx, H. canis, and Helicobacter sp. strain CLO-3). Besides this, we could also detect cholesteryl acyl glucoside in H. acinonyx, cholesteryl glucoside inHelicobacter sp. strains Bird-B and -C, and cholesteryl phosphatidyl glucoside in ''H. rappini'' and Helicobacter sp. strain Bird-C. A selective accumulation of free cholesterol was observed in the neutral lipid fractions. On the basis of the detection of CGs in 11 of the 13 species studied so far, the presence of CGs appears to be a characteristic feature of the genus Helicobacter. In view of this and also because of a simple and rapid detection method described herein, the CGs can be used as a valuable chemotaxonomic marker.

Two strains of Staphylococcus aureus (Newman and Tazaki) and their derived L-forms were cultured in serum-containing broth and the differences in their lipid compositions were analyzed. Cardiolipin accounted for more than 50% of the total phospholipid phosphorus in L-forms, but for less than 25% in parent bacteria. The cardiolipin content of L-forms was very high through all growth phases, although it increased gradually as growth proceeded. Significant amounts of cholesterol and its esters were present in parent strains and L-forms, all of which incorporated serum cholesterol into the cell membrane. On the other hand, they could be detected in the L-forms but not in the parent strains when they were cultured in serum-free broth. To examine the ability of L-forms to synthesize cholesterol, the cholesterol content of L-forms cultured in serum-free broth was compared with that of the medium. The results indicated that staphylococcal Lforms could synthesize cholesterol and its esters. These differences in lipid composition suggested that modification of membrane lipids may occur as an adaptational change in response to the disappearance of the cell wall.Bacterial L-forms which can be grown under appropriate conditions lack cell walls but have many of the biological characteristics of parent bacteria. The plasma membrane, as a result of being directly exposed to the external millieu, might be expected to undergo changes in both structure and function. Especially, stable L-forms which cannot revert to parent strains are more likely to acquire a membrane different from that of parent strains. Chemical analysis of stable L-form membrane, therefore, should provide information about the adaptational changes in the cell surface of a microorganism. There have been few reports of differences in membrane components between parent bacteria and derived L-forms (2, 19,26). Much of the attention has been focused, instead, on the presence or absence of cell wall substances in L-forms (16, 20,24) and the mode of L-form proliferation (5, 18). The authors have made a study on the differences in membrane components between Staphylococci and staphylococcal L-forms.The present work examines the phospholipid and neutral lipid composition of two stable L-forms of S. aureus and makes a comparison of these with those of the 435

Adaptation of Staphylococcus aureus to a change in salinity was studied by estimating the intracellular content of water and proline after alteration of the salt concentration of the culture medium. The intracellular water content of S. aureus cultured in normal broth was 1.70 g/g (dry weight). After transfer to 1.8 M NaCl-containing broth, the water content decreased to 0.80 g/g (dry weight) within 1 min. After changing the salt concentration of the medium, intracellular free proline (assumed to be one of the osmoregulators in S. aureus) increased gradually from 0 to 1,400 umol/g (dry weight) during 30 min of incubation at 370C. The water content rose to 0.88 g/g (dry weight) in 30 min. Proline was not taken up at 0 to 40C, suggesting that the process was one of active transport. The salt tolerance of S. aureus, therefore, appears to occur initially by dehydration of the cell after transfer from a medium of low salinity to one of high salinity and then by accumulation of proline, which carries water into the cell with it. o. 3 S.A.

Yersinia enterocolitica is capable of growing in a broad range of temperatures from 4 to 45 C. How this organism alters its membrane lipids in response to the change of growth temperature is very interesting. The fatty acids of membrane lipids of cells cultured at 5, 15, 25 and 37 C were analyzed and the physical states of these membrane lipids were characterized. The major phospholipids of this bacterium were phosphatidylethanolamine, phosphatidylglycerol, cardiolipin, lysophosphatidylglycerol and lysophosphatidylethanolamine.No significant difference in phospholipid composition in response to culture temperatures was observed. It was reported in our previous paper that the major fatty acids of membrane phospholipids of Y. enterocolitica were C15: 0, C16:0, C16: 1, cyclopropane C17: 0 and C18: 0. Some differences in the fatty acid composition were, however, observed with the change of culture temperature. When the culture temperature was raised, the saturated and cyclopropane fatty acids substantially increased and the unsaturated ones decreased. A. reverse phenomenon was observed when culture temperature was lowered. From the viewpoints of membrane physical state, adaptational changes were analyzed using a nylon microcapsule method. Phase transition in membrane lipids of cells grown at each culture temperature took place in the range of about 5 C below and about 10 C above the culture temperature.It is, therefore, considered that Y. enterocolitica maintains its membrane rigidity and fluidity in response to growth temperature by changing the membrane fatty acid composition.