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1.
Casadesús J 《BioEssays : news and reviews in molecular, cellular and developmental biology》2007,29(12):1189-1191
Cell-wall-less bacterial variants, or L-forms, have been described in many bacterial species under laboratory conditions, in infected eukaryotic cell cultures and inside animals. Of special interest for human health is the formation of L-forms as a consequence of specific antibiotic treatments, and the potential involvement of L-forms in persistent and relapsing infections. An old enigma about L-forms is how they can divide in the absence of cell wall synthesis, since septum formation is an essential requisite for cell division. However, the classical definition of L-forms as cell-wall-less bacterial variants may need a revision to accommodate recent observations by Richard d'Ari and coworkers: genetic and biochemical evidence indicates that E. coli L-forms induced by beta-lactam antibiotics do contain small amounts of peptidoglycan, essential for their growth and probably required for septum formation. If these observations are extrapolated to all known L-forms, the very concept of cell-wall-less bacteria may need revision, and be restricted to mycoplasmas and their relatives. 相似文献
2.
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 L-forms 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. 相似文献
3.
免疫酶技术鉴定 El Tor 型霍乱弧菌稳定 L 型 总被引:2,自引:0,他引:2
细菌稳定 L 型的形态、培养特性以及生化反应常与原菌不同,其菌落在盐水中不能乳化,故不能通过玻片凝集测定其抗原。对于这种一时不能回复为原菌的 L 型很难进行鉴定。本文采用免疫酶技术对由鳝鱼和鲫鱼胆汁诱导的 El Tor 型霍乱弧菌稳定 L 型进行了鉴定。实验证明 L 型的细胞壁可有不同程度的缺失,稳定 L 型仍可能有少量“O”抗原存在。PAP 法比较敏感,即使少量抗原亦可以检出。 相似文献
4.
Ultrastructure of Brucella abortus L-forms induced by penicillin in a liquid and in a semisolid medium 总被引:1,自引:1,他引:0
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Brucella abortus L-forms were induced by 5.0 or 10.0 mug of penicillin/ml in a broth medium containing 0.3 m sucrose, and in a semisolid medium containing 10% calf serum and 20.0, 40.0, or 60.0 mug of penicillin/ml. After 96 hr of incubation, L-forms of various sizes and shapes were observed. Basic structures of the L-forms were similar whether induced in liquid or semisolid medium. L-forms had two "unit" membranes, each consisting of two outer dense layers separated by a lucent layer. A few large, irregularly shaped organisms in penicillin-treated broth cultures had additional surface material and were referred to as "transitional" forms. In contrast with L-forms, the bacterial cells were fairly uniform in size and shape, were smaller, and had a more complex cell wall structure. Small bodies limited by a "unit" membrane were present within and around numerous L-forms from liquid and semisolid medium cultures. Other internal membranous structures were also seen in some L-forms. Most Brucella L-forms described in this paper reverted to bacteria in the absence of penicillin and were structurally characteristic of unstable L-forms. 相似文献
5.
L-forms of Staphylococcus aureus, Streptococcus faecalis, Listeria monocytogenes and Salmonella typhy and their parent bacteria were examined for biological properties and compared with their parental forms. Some L-forms differed from their parent bacteria and required a longer incubation period. 相似文献
6.
Dienes L 《Journal of bacteriology》1970,104(3):1378-1385
A large pleomorphic gram-negative bacillus developed as a contaminant on blood-agar. Spores were formed in one culture. L-forms were produced with penicillin on blood-agar with 2.5% NaCl; they grew well when transplanted to agar with 0.5% NaCl. After several transplants and long incubation of the L-forms without penicillin, in three transplants small gram-negative pleomorphic bacilli grew, but no L-forms. This occurred once on blood-agar and twice on 30% gelatin. The growth obtained from these small bacilli was similar in morphology and in the physical properties of the organisms to the altered L-forms of Proteus and Salmonella. Multiplication of the pleomorphic organisms and development of branching filaments from the round forms was apparent. The original large gram-negative bacillus was regularly recovered from the L-forms, and was recovered several times from the descendants of the small bacilli. These observations are essentially similar to those made with L-forms of Proteus and with an L-form studied in 1952, indicating alterations in L-forms of bacteria which do not produce B type L-forms. 相似文献
7.
The chemical composition of the membranes of protoplasts and L-forms of Staphylococcus 总被引:3,自引:0,他引:3
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Membrane fractions were prepared from Staphylococcus aureus H and 100 after dissolution of the cell walls by a lytic enzyme from Streptomyces griseus. Membranes were also prepared from the L-forms derived from the same strains. The membranes were analysed for protein, lipid, carbohydrate and RNA contents, and the fatty acid composition of the lipids was determined. A branched-chain saturated C(15) acid was the major component in all samples, and the correspondence between L-forms and parent bacteria was fairly close. The lipids were separated into non-polar-lipid, glycolipid and phospholipid fractions; the L-forms contained a little more neutral lipid and much more glycolipid than the parent bacteria. In all membranes the glycolipid, which accounted for all the carbohydrate present, was a diglucosyl diglyceride. The major phospholipids of the protoplast membranes were phosphatidylglycerol and some lipoamino acids (lysine and a little alanine). On the other hand, diphosphatidylglycerol was the chief phospholipid found in L-form membranes. 相似文献
8.
C. Weibull 《Folia microbiologica》1967,12(3):214-219
By comparing three methods for disruption of normal bacteria and bacterial L-forms (process ing in the Ribi-Sorvall Cell Fractionator
or in the X-press of Edebo, and osmotic shock), it was shown that the outcome of fractionation experiments with disintegrated
bacteria is highly influenced by the disintegration method employed. The localization of seven enzymes in normal Proteus bacteria
and Proteus L-forms was studied. The experimental results indicate that the succinic dehydrogenase and NADH oxidase are located
in the membranous part of both types of organisms, the glucose-6-phosphate and isocitric dehydrogenase, the fumarase, the
catalase, and the acid phosphatase in the “soluble” protoplasm. 相似文献
9.
Mixtures of various combinations of Lysostaphin protoplasts and stable L-forms of Staphylococcus aureus, which have different markers for drug resistance, were treated with polyethylene glycol (PEG) to examine the development of doubly resistant fusion products (fusants). To recover doubly resistant colonies as L-forms, they were incubated in 4.5% NaCl-brain heart infusion (BHI) broth containing penicillin G (PCG) for enrichment culture and cultured in PCG-4.5% NaCl-BHI agar medium (method 1), while to recover doubly resistant fusants as L-forms and coccal forms, they were grown on reversion medium (R medium) which causes reversion of protoplasts or fusants to parent type cells, and then cultured on assay media, i.e., R medium, BHI agar medium or PCG-4.5% NaCl-BHI agar medium (method 2). Under both experimental conditions, doubly resistant fusants developed as L-form cells by PEG treatment of pairs of protoplasts carrying the chloramphenicol (CP)-resistance plasmid and L-forms having chromosomal resistance to streptomycin (SM). In the reverse combinations, i.e., protoplasts showing chromosomal SM-resistance and L-form cells carrying the CP-resistance plasmid, the first method gave no doubly resistant colonies. By the second method, without enrichment culture on R medium, the latter combination gave doubly resistant fusants as L-form, coccal-type and mixed-type colonial forms, while when the PEG-treated mixture was enriched on R medium, fusants were obtained exclusively as the coccal type on either R medium or BHI agar assay medium. Neither of the methods yielded colonies of doubly resistant fusants on PEG-treatment of pairs of protoplasts and L-forms both of which were chromosomal, but with different drug resistances. These results show that PEG-induced cell fusion between protoplasts and L-forms of S. aureus, unlike the fusion between protoplasts or between L-forms, resulted in transfer of the drug resistance controlled by the plasmid to the fusion products. The fusants obtained were L-forms in method 1, and coccal type in the method 2. 相似文献
10.
Sarabelie Madoff 《Current microbiology》1979,2(1):43-46
Factors excreted into the medium by various bacteria and fungi exert a significant effect on the growth and revertibility
of bacterial L-forms. Studies with L-forms ofHaemophilus influenzae have been facilitated by a strain ofNeisseria perflava, which not only promotes the growth of the L-forms on media of normal osmolarity (horse blood agar), but also enhances the
revertibility of the L-forms to the parent bacterium. L-forms derived fromN. perflava also exhibit this growth-enhacing property, an effect that does not appear to be related to X and V factors. Preliminary
characterization of the active component produced byNeisseria perflava indicates that it is present in broth filtrate, diffusible through agar, heat labile, and of large molecular size. 相似文献
11.
Z N Kochemasova G P Shul'tser N G Kassirskaia V I Burtsev D Ia Bakanova 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》1975,(4):103-105
The authors present the data concerning the study of 200 patients suffering from chronic pyelonephritis; in 28 of these L-forms of bacteria were revealed in the urine. Of 46 L-cultures isolated from these patients 13 reversed into bacterial forms, 8 failed to reverse and were referred to the stable L-forms; the rest 25 L-cultures perished during the 8th--10th passage. This led to a supposition that the relapses and exacerbations of the infectious process in pyelonephritis were associated with the change of the L-forms into bacterial ones, and that the persistence of the L-forms in the kidney tissue promoted the maintenance of the chronic process. 相似文献
12.
Jana Jass Lisa E. Phillips Eunice J. Allan J.W. Costerton Hilary M. Lappin-Scott 《FEMS microbiology letters》1994,115(2-3):157-162
Abstract Comparisons of growth and surface colonisation of Enterococcus faecium L-forms and their cell-walled forms were undertaken to produce information about their ability to form sessile cells. The growth of L-forms in liquid culture was slower than that of the parent. This was reflected in their longer lag phase and slower specific growth rates: 0.16 h−1 for the L-form and 0.81 h−1 for the parent. Although E. faecium L-forms attached to a silastic rubber surface, the attached population density was 10–100-fold less than that of the parent. Confluent biofilms on the silastic surfaces were not observed for either bacterial form. Comparison of the attachment of E. faecium L-form and parent may provide important information on how bacteria overcome host defence mechanisms and antibiotic treatment. 相似文献
13.
New data are presented on the ability of different aerobic spore-forming bacteria isolated from the organism of urological patients to produce L-forms of these microorganisms in the presence of penicillin and ampicillin. Bacillus cereus is shown to be the most resistant to these antibiotics. 相似文献
14.
目的研究铜绿假单胞菌(PA)及L型诱导巨噬细胞凋亡的能力,比较二者的差异。方法用生物素断端标记(TUNEL)法检测PA及L型感染巨噬细胞2、4、8、12、16和20h后各时间段的细胞凋亡率,Giemsa染色观察细胞凋亡情况,硝酸还原酶法检测培养液中一氧化氮(NO)的浓度变化。结果 PA及L型能诱导巨噬细胞发生凋亡,与对照组比较差异有统计学意义(P〈0.05);L型诱导细胞的凋亡率弱于原菌(P〈0.05);PA及L型感染组培养液NO浓度较对照组明显升高(P〈0.05)。结论 PA及L型可诱导巨噬细胞发生凋亡,L型较其原型诱导细胞凋亡的能力弱,NO可能在巨噬细胞凋亡中发挥一定作用。PA及L型可通过诱导巨噬细胞凋亡,发挥致病作用。 相似文献
15.
分枝杆菌L型感染与肺癌患者红细胞免疫功能改变的相关性 总被引:1,自引:0,他引:1
目的:研究分枝杆菌L型血行感染与肺癌患者红细胞免疫功能改变的相关性.方法:溶血离心培养法和滴片法检测血液中的分枝杆菌L型,常规方法测定红细胞沉降率(ESR)、红细胞C3b受体花环率(C3bRR)、免疫复合物花环率(ICRR)、血清红细胞C3b受体花环促进率(RFER)和抑制率(RFIR).结果:TBL( )与TBL(-)肺癌患者相比,C3bRR和ICRR两项指标均明显降低.TBL( )肺癌与TBL(-)肺癌患者相比,ESR增快更为显著.TBL(-)较TBL( )之RFER值的降低更为明显.RFIR差异未见有显著性.结论:分枝杆菌L型血行感染影响肺癌患者血沉和红细胞免疫功能改变. 相似文献
16.
Folia Microbiologica - Continuing previous experiments (Bla?-kovi? & Raus, 1959) the authors attempted to induce L-forms of bacteria in the nasopharynx of rats by penicillin... 相似文献
17.
目的 探讨嗜酸乳杆菌(L. acidophilus)对肠道致病菌及其L型菌的抑菌作用,为临床开发L. acidophilus活菌制剂提供实验依据。方法 采用肉汤稀释法,检测L. acidophilus 36 h发酵上清液对肠道致病菌及其L型菌吸光度值的影响,计算抑菌率,探讨乳杆菌的抑菌活性。结果 3个浓度的L. acidophilus发酵上清液对3种常见肠道致病菌(致病性大肠埃希菌、伤寒沙门菌、痢疾志贺菌)及其L型菌均有不同程度抑菌作用,其中原液浓度抑菌作用最强。结论 L. acidophilus是一种可用于治疗多种肠道致病菌及其L型菌感染引起肠道疾病的微生态制剂,其代谢产物发挥抑菌作用是其机制之一。 相似文献
18.
In penicillin-susceptible bacteria, penicillin causes growth of a small fraction of cells as wall-deficient forms if an appropriate osmoprotection is provided (unstable L-forms). A subfraction of human serum high density lipoprotein (HDL3) was shown to have the ability to inactivate unstable L-forms of Staphylococcus aureus. The active principle was distinguishable from the well-documented trypanosome lytic factor 1 with respect to density, size, and other properties. This L-form cytotoxicity therefore seems to represent a novel antimicrobial entity in human serum. 相似文献
19.
Penicillin-binding proteins and carboxypeptidase/transpeptidase activities in Proteus vulgaris P18 and its penicillin-induced stable L-forms 总被引:1,自引:0,他引:1
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The originally penicillin-induced, wall-less stable L-forms of Proteus vulgaris P18, isolated by Tulasne in 1949 and since then cultured in he absence of penicillin, have kept the ability to synthesize the seven penicillin-binding proteins and the various DD- and LD-peptidase activities found in the parental bacteria and known to be involved in wall peptidoglycan metabolism. The stable L-forms, however, secrete during growth both the highly penicillin-sensitive, DD-carboxy-peptidase-transpeptidase penicillin-binding protein PBP4 (which in normal bacteria is relatively loosely bound to the plasma membrane) and the penicillin-insensitive LD-carboxypeptidase (which in normal bacteria is located in the periplasmic region). 相似文献
20.
Induction of Bacillus brevis L-forms 总被引:3,自引:1,他引:2
L-forms of Bacillus brevis were induced and maintained in L-phase medium supplemented with inactivated horse serum with a combination of penicillin (80 u/ml) and cephalosporin (5 μg/ml) in liquid medium and penicillin (200 u/ml) in diphasic culture. These L-forms failed to grow on solid media. 相似文献