Ultrastructural characteristics of the human synoviocytes

The purpose of this study was to identify, by the scanning electron microscopy, the behaviour of the different cell types in the normal human synovial intima, in order to obtain information useful for interpreting pathological changes in the synovium. Our observations revealed that, in numerous areas of the synovial membrane (adipose or fibrous type), the synoviocytes were dispersed and the intercellular matrix, covered only by the cytoplasmic processes of cells deeply located, was in direct contact with the joint cavity. In the areolar type of the synovium the synoviocytes were more numerous; they tended to concentrate to give the appearance of a continuous tissue; but between the cells very large intercellular spaces were usually present. In this latter membrane type we identified the two main cellular types of the synoviocytes: A and B. B-synoviocytes were the predominant cell type of the synovium. These cells were characterized by long cytoplasmic processes, perpendicularly directed towards the joint cavity. Both the cellular body and the cytoplasmic processes were covered by small blebs and vesicles of various size. The A-synoviocytes were a small minority, rarely dispersed between the B-synoviocytes. They were characterized by numerous membrane infoldings which delimited intracellular canaliculi of various depth. Our ultrastructural observations demonstrated that, in normal conditions, the B-synoviocyte must be considered as a constitutive element which characterized the synovial intima, responsible for the specific structure of the interstitial tissue and for the regulation of the composition of the synovial fluid.(ABSTRACT TRUNCATED AT 250 WORDS)     

Unique localization of protein gene product 9.5 in type B synoviocytes in the joints of the horse.

Fibroblast-like (Type B) synoviocytes are cells in the synovial membrane that are responsible for production of both synovial fluid and the extracellular matrix in the synovial intima. Immunostaining of the horse synovial membrane for protein gene product (PGP) 9.5, which is a neuron-specific ubiquitin C-terminal hydrolase, demonstrated selective localization of the immunoreactivity in a synoviocyte population different from acid phosphatase-positive Type A synoviocytes. The immunoreactive cells were lined up in the synovial intima and extended dendritic processes towards the joint cavity to form a dense plexus on the surface. Electron microscopic examination clearly identified the PGP 9.5-immunoreactive cells as Type B synoviocytes characterized by developed rough endoplasmic reticulum and free ribosomes. Immunoreactivity for PGP 9.5 was diffusely distributed throughout the cytoplasm, including the tips of fine processes. Western and Northern blot analyses could not distinguish the corresponding protein and mRNA obtained from the brain and synovial membrane. The existence of the neuron-specific PGP 9.5 in Type B synoviocytes suggests a common mechanism regulating the protein metabolism between neurons and synoviocytes, and also provides a new cytochemical marker for identification of the cells.     

Local inhibitor of the crayfish telson-flexor motor giant neurons: morphology and physiology

The motor circuits that control telson flexion in the crayfish (Procambarus clarkii) include a curiously arranged sub-circuit: a premotor 'command' neuron excites a motor neuron via a trisynaptic pathway, but also inhibits (and prevents firing of) the motor neuron via a shorter latency pathway (Kramer et al. 1981 a). The premotor and motor neurons in this circuit have been previously identified (Kramer et al. 1981 a; Dumont and Wine 1985a, b; see Fig. 1). We have now identified a local interneuron that inhibits the motor neurons. The cell we studied is called the 'C' cell because of its distinctive structure (Figs. 2, 3). A single pair of bilaterally homologous C-cells was found in the last (6th) abdominal ganglion. The C-cells are invariably dye coupled to one another following injections of lucifer yellow into either one of them, and are frequently dye coupled to smaller axons in the 2nd, 3rd, and 6th nerves. In addition, some of the extensive branches of the C-cell extend out into the 6th nerve, where they are in close proximity to the axons of the motor neurons they inhibit (Fig. 3). Two kinds of evidence established that the C-cell directly inhibits the motor neurons. First, when simultaneous recordings were made from the C-cell and the motor neurons, spikes in the C-cell, no matter how evoked, were invariably followed, within 1.5 ms, by depolarizing IPSPs in the motor neuron (Fig. 6). Second, when the C-cell was hyperpolarized so that it could not fire, that same IPSP in the motor neuron was abolished (Fig. 6). The inhibitory pathway to the motor neurons must be fired at short latency in order to prevent firing caused by the trisynaptic excitatory input (Fig. 1). The C-cells were fired at short latency (less than 3 ms) by impulses in either of the escape command cells (Fig. 4), and at even shorter latency by impulses in the Segmental Giant of the 6th ganglion (SG6) (Fig. 5). It has been established elsewhere that the SGs are a major output pathway of the escape command cells; our results suggest that they may be the pathway for command-evoked firing of the C-cell. The C-cells are also excited by two descending, non-giant, flexion premotor neurons, called I2 and I3 (Fig. 5). The EPSPs from a single I2 or I3 impulse were subthreshold, but temporal and spatial summation of EPSPs from the non-giant pathway sometimes fired the C-cells.(ABSTRACT TRUNCATED AT 400 WORDS)     

In vivo visualization of individual neurons in arthropod ganglia facilitates intracellular neuropil recording

Summary A simple method for the in vivo visualization of dye filled cells by laser illumination is used to characterize neurons in situ in the segmentai ganglia of the locust and the crayfish (Fig. 1). Neuron visualization provides the structural information necessary for identification of cells during an ongoing physiological experiment (Figs. 2, 3). Sequential penetrations of soma and neuropil as well as simultaneous double neuropil penetrations of spiking and nonspiking cells are facilitated by the visual control afforded by neuron visualization (Figs. 4, 5, 6). Furthermore, neuron visualization allows the sampling of cellular properties at multiple, predetermined sites in the dendritic and axonal arbors of identified neurons (Fig. 7) and aids in establishing synaptic connectivity through double neuropil recordings (Fig. 8).     

B-cells of the synovial membrane. II. Differentiation during development of the synovial cavity in the mouse

Summary Study of pre- and postnatal development of the metatarsophalangeal joint of the mouse shows that the synovial cavity (SC) forms before any differentiation of the synovial mesenchyme. The primitive cleft results from degradation of a thin vascular mesenchymal layer in direct contact with the chondrogenic layers. Differentiation of the synovial membrane coincides with clarification of the SC (3rd to 6th day of postnatal life). When dilatation of the SC occurs (6th to 8th day), the two intimal cells types (A- and B-cells) are well identified. The B-cells already show typical features at day 6; their content of typical dense secretory vesicles is comparable to that of the adult B-cells at day 13. The specific secretory function of B-cells could be correlated with the particular structure of the intimal interstitial tissue and could account for the origin of some protein(s) of the synovial fluid.ERA 178 (Neuroendocrinologie Comparée) du CNRS et INSERM     

Oncostatin M stimulates urokinase-type plasminogen activator activity in human synovial fibroblasts

Cytokine regulation of synovial cell function has been considered to be involved in the pathogenesis of rheumatoid arthritis. Synoviocyte urokinase-type plasminogen activator (u-PA) expression may be relevant to the tissue remodelling, as well as to the cell migration and transformation occurring in rheumatoid joints. We report here that purified recombinant human oncostatin M (greater than or equal to approximately 0.2 U/ml = 1 pM) stimulated within six hr the u-PA activity of non-rheumatoid synovial fibroblast-like cells and raised their u-PA mRNA levels. Oncostatin M could augment PGE2 production and DNA synthesis in these cells; however, the increase in PGE2 was small compared with that caused by IL-1. Since oncostatin M is produced by immune cells, it may have a role in immune and inflammatory reactions by interacting with fibroblast populations, such as synoviocytes, in the manner described.     

Electron microscope investigation of the evolutionary stages of the trophozoite of Didymophyes gigantea (Sporozoa, Gregarinida). III. The fine structure of the epicyte with emphasis on the contractile elements (author's transl)

The fine structure of the epicyte of D. gigantea was investigated. The motility of the gregarine and the contractile elements are described. Four essential types of movements can be observed in this gregarine: (1) rolling up and pendular movements, (2) locomotion by gliding forward, (3) cytoplasmic streaming (Fig. 1), (4) peristaltic contractions (Fig. 2) which seem to be accompanied by the contraction of annular myonemes (Fig. 2). The epicyte is formed by the folding of the parasitic cell wall which is made from three membranes (Figs. 3 and 4). At the top of each fold one can see apical struts between the outer and middle membrane and apical filaments under the inner membrane (Fig. 3). In addition, the epicytic folds are covered by a cell coat which is made from tubular structures (Fig. 5). At the base of the epicytic folds can be observed the basal lamina (Fig. 3) composed of very fine fibrillar material with an average thickness of 2.5 nm (Fig. 6). These fibrils are oriented in the longitudinal axis of the gregarine. Beneath the epicytic fold in the ectoplasm are found the annular myonemes with a width of up to 0.5 micrometers (Fig. 7). They are composed of many fine fibrils with an average thickness of 5 nm. In young trophozoites, the myonemes also contain microtubuli (Fig. 8). Between the epicytic folds, the cell wall is interrupted by three different types of vesicles: the vesicles with an electrondense content (Fig. 9), the three-membranous vesicles (Fig. 10), and the hose-shaped vesicles (Fig. 11). Glycerol-extraction of the parasites was performed in order to define the contractile structures. After extraction the annular myonemes are difficult to recognize (Fig. 13). When ATP is added, the gregarine does not contract but the myonemes reappear after 3 to 4 min (Fig. 14). Differences can also be observed in the myoneme structure using electron microscopy: After extraction, the myonemes are composed of a very limp fibrillar network (Fig. 15) which becomes very dense after the action of ATP (Fig. 16). Glycerol extraction does not disturb either the apical struts and apical filaments or the fibrils of the basal lamina (Figs. 15--17). In addition, cytoplasmic fibrillar structures appear after glycerol extraction (Figs. 15 and 16). The experimental and electron microscope results indicate that the motility of the gregarine depends upon four different systems: (1) the ectoplasmic annular myonemes, (2) the apical structures in the undulating epicytic folds, (3) the cytoplasmic fibrils, and (4) the basal lamina.     

Comparative anatomical study of the synovial membrane in representatives of 4 classes of terrestrial vertebrate

The synovial membrane (SM) of some representatives of four terrestrial vertebrate classes was studied by means of scanning electron microscope (SEM). The figures of SM of the mammals (man, mini-pig), birds (fowl, Gallus domesticus L.), reptiles (lizard, Lacerta viridis Laur. and turtle, Testudo graeca L.) and amphibians (frog, Rana esculanta L.) are documented. The SM of all animal species investigated presents a great locally variable appearance in form and surface arrangement of the living cells. The surface of synoviocytes is mostly very rough, forked, the cells having a plenty of wart-like, spiny-like or leaf-like microvilli, with cytoplasmic projections protruding from cell bodies. The largest possible functional surface of SM in mammals is formed by multiple villi and folds, whereas in other animal classes--by a specific arrangement of the lining cells. Locally variable appearance of synoviocytes from human and rabbit joints was described by Date (1979); we have documented the same in birds, reptiles and amphibians, as well. Three characteristic types of locally variable appearance of the surface lining cells were picked out in representatives of the every animal class cited. These cells correspond to the histological types, classified by Key. Beside these basic types, a number of transitory cells appear, that increase the diversity of the appearance of the lining cells in different regions of the SM. We may conclude that all the synoviocytes present the largest possible functional surface, although their external form differs. Their cytoplasm contains all sorts of organelles necessary for synthesis and secretion of mucopolysaccharides of the synovial liquid, as well as for the resorption and phagocytosis.     

Epstein-Barr virus DNA XII. A variable region of the Epstein-Barr virus genome is included in the P3HR-1 deletion.

The P3HR-1 subclone of Jijoye differs from Jijoye and from other Epstein-Barr virus (EBV)-infected cell lines in that the virus produced by P3HR-1 cultures lacks the ability to growth-transform normal B lymphocytes (Heston et al., Nature (London) 295:160-163, 1982; Miller et al., J. Virol. 18:1071-1080, 1976; Miller et al., Proc. Natl. Acad. Sci. U.S.A. 71:4006-4010, 1974; Ragona et al., Virology 101:553-557, 1980). The P3HR-1 virus was known to be deleted for a region which encodes RNA in latently infected, growth-transformed cells (Bornkamm et al., J. Virol. 35:603-618, 1980; Heller et al., J. Virol. 38:632-648, 1981; King et al., J. Virol. 36:506-518, 1980; Raab-Traub et al., J. Virol. 27:388-398, 1978; van Santen et al., Proc. Natl. Acad. Sci. U.S.A. 78:1930-1934, 1980). This deletion is now more precisely defined. The P3HR-1 genome contains less than 170 base pairs (and possibly none) of the 3,300-base pair U2 region of EBV DNA and is also lacking IR2 (a 123-base pair repeat which is the right boundary of U2). A surprising finding is that EBV isolates vary in part of the U2 region. Two transforming EB viruses, AG876 and Jijoye, are deleted for part of the U2 region including most or all of a fragment, HinfI-c, which encodes part of one of the three more abundant cytoplasmic polyadenylated RNAs of growth-transformed cells (King et al., J. Virol. 36:506-518, 1980; King et al., J. Virol. 38:649-660, 1981; van Santen et al., Proc. Natl. Acad. Sci. U.S.A. 78:1930-1934).     

Light and Electron Microscopic Investigation of Equine Synovial Membrane

Light and electron microscopic examination was made on equine synovial membrane from 23 healthy joints, nine joints with synovitis caused by intraarticular fracture and 10 joints with synovitis caused by osteochondrosis dissecans. Histologically as well as ultrastructurally the equine synovial membrane from healthy joints was of principally the same character as described in other species. Three types of synovial membrane — areolar, fibrous and adipose — and two types of lining cell were distinguished histologically. Ultrastructurally three types of lining cells were distinguished: A and Β type and an intermediate cell type. In healthy joints they were loosely arranged, parallel to the joint surface in an intercellular matrix, which was in direct continuity with the joint space. In joints with intraarticular fracture there was mild inflammation of the synovial membrane. There was elongation and hyperplasia of the lining cells with a relative increase in type A cells. The cell surface of lining cells was increased through filopodia. There was also an increase in cytoplasmic organelles i.e. hyperplasia of rough endoplasmic reticulum and Golgi complexes in Β type cells and an increase in lysosomes, and increased numbers of vesicles of varying types in A cells. In joints with osteochondrosis dissecans the lining cell hyperplasia and the inflammation in the synovial membrane were more prominent. Ultrastructurally the same alterations as in the previous group were seen including a relative increase in the number of A cells but degenerative changes were common in the lining cells. These changes were dilatation and vesiculation of rough endoplasmic reticulum, mitochondrial condensation, dilatation of the nuclear envelope and loss of plasma membranes, leading to disintegration of cells.     

脱乙酰壳多糖处理增加人参细胞皂苷的累积和皂苷合成关键酶基因的转录

脱乙酰壳多糖处理可以诱导人参细胞产生H2 O2 ,增加人参皂苷的累积 ,提高鲨烯合酶 (squalenesynthase,GSS)与鲨烯环氧酶 (squaleneepoxidase,GSE)基因的转录水平。质膜NADPH氧化酶的抑制剂DPI,H2 O2 的淬灭剂DMTU与DHC可以抑制脱乙酰壳多糖的这些效应 ,暗示脱乙酰壳多糖可以活化质膜NADPH氧化酶而产生H2 O2 ,H2 O2 进而作为第二信使诱导gss与gse基因转录以及皂苷的合成。质膜钙通道抑制剂LaCl3与内质网钙通道抑制剂RR ,以及蛋白激酶抑制剂K2 5 2a都能削弱脱乙酰壳多糖促进皂苷积累和gss、gse转录的效应 ,说明胞内Ca2 浓度的升高与蛋白质磷酸化都参与了脱乙酰壳多糖诱导的gss、gse的转录以及皂苷的合成     

Proton-sensing G protein-coupled receptor mobilizes calcium in human synovial cells

Lowered extracellular pH in a variety of tissues is associated with increased tissue destruction and initiation of inflammatory processes. Although the acid-sensing receptors described previously are ion channels, we describe a G protein-coupled proton-sensitive receptor that stimulates Ca(2+) release from intracellular stores in a tumor-derived synoviocyte cell line (SW982) and in primary cultures of human synovial cells from patients with inflammatory arthropathies. We established a link between proton-dependent receptor activation and intracellular Ca(2+) mobilization by demonstrating 1) dependence on the integrity of the intracellular Ca(2+) store, 2) independence from extracellular Ca(2+), and 3) proton-induced production of inositol phosphate and 4) by abolishing the effect with GTPase inhibitors. We propose that this G protein-coupled acid-sensing receptor linked to intracellular Ca(2+) mobilization in synoviocytes can contribute to downstream inflammatory and cellular proliferative processes in synovial fibroblasts. The acid-sensing receptor has distinct characteristics as a metabotropic G protein-coupled receptor on human synoviocytes in this emerging new class of receptors.     

Change of genetic expression by physical compression forces

Despite intense investigation of transmembrane signalling mediated by lymphocyte surface molecules, the subcellular mechanisms responsible for these phenomena remain poorly understood (Kishimoto, T. et al., 1983). In the present study, an answer for the mechanism is demonstrated by using human B blastoid cell line (CESS) which has IgG and Interleukin 6 (IL-6) receptors on the cell surface and produces IgG in response to IL-6 without any requirement for proliferation (Muraguchi, A. et al., 1981).     

黄化水稻幼苗转绿期AOX1基因家族的表达与功能分析

完全黄化的水稻幼苗叶片在持续光照下总呼吸速率、交替途径的速率以及交替途径在总呼吸中的比值均上升,但以水稻AOX1基因家族3个成员的特异性片段为探针,仅观察到其中AOX1c转录本的增加。交替途径的专一性抑制剂SHAM可以降低水稻幼苗在持续光照过程中的相对光合放氧速率与叶绿素含量。同时,水稻黄化幼苗光照前黑暗处理时间越长,在恢复光照后交替途径能力的增加越显著,表现了转绿进程与交替途径之间的相关性。推测加强交替途径可能是植物缓和能量和物质需求矛盾的一个重要调控机制。     

Cytochrome P450 reductase (POR)as a ferroptosis fuel

Oxygen,iron,and polyunsaturated fatty acids (PUFAs;fatty acids containing more than one double bond) are all bene-ficial to our cellular lives.Incorporation of these components into cellular processes,however,comes at a cost:the bis-allylic structure of PUFAs and the enrichment of cellular environments with iron and oxygen render PUFA-containing phospholipids (PUFA-PLs) particularly susceptible to per-oxidation (Yang and Stockwell,2016).Accumulation of lethal amounts of lipid peroxides in cell membranes leads to a form of cell death known as ferroptosis (Dixon et al.,2012;Stockwell et al.,2017;Stockwell and Jiang,2020).Conse-quently,cells are equipped with strong antioxidant defense systems that constantly dissipate toxic lipid peroxides gen-erated in cellular membranes,thereby maintaining cell via-bility and homeostasis (Zheng and Conrad,2020).The most powerful anti-ferroptosis defense system is believed to be mediated by glutathione peroxidase 4 (GPX4),a glutathione peroxidase that uses glutathione as its cofactor to reduce lipid hydroperoxides to non-toxic lipid alcohols (Fig.1)(Zheng and Conrad,2020).A variety of ferroptosis inducers(FINs) act to inactivate GPX4 or deplete glutathione,causing an imbalance between the production and detoxification of lipid peroxides that subsequently induces ferroptotic cell death (Yang et al.,2014).Genetic ablation of GPX4 can have the same effect (Friedmann Angeli et al.,2014).     

Physiology and pharmacology of acetylcholinergic responses of interneurons in the antennal lobes of the mothManduca sexta

1. Neurons in the antennal lobe (AL) of the moth Manduca sexta respond to the application, via pressure injection into the neuropil, of acetylcholine (ACh). When synaptic transmission is not blocked, both excitatory (Fig. 2) and inhibitory (Fig. 3) responses are seen. 2. Responses to ACh appear to be receptor-mediated, as they are associated with an increase in input conductance (Figs. 2B and 3B) and are dose-dependent (Fig. 2 C). 3. All neurons responsive to ACh are also excited by nicotine. Responses to nicotine are stronger and more prolonged than responses to ACh (Fig. 4C). No responses are observed to the muscarinic agonist, oxotremorine (Fig. 4 B). 4. Curare blocks responses of AL neurons to applied ACh, while atropine and dexetimide are only weakly effective at reducing ACh responses (Figs. 5 and 6). 5. Curare is also more effective than atropine or dexetimide at reducing synaptically-mediated responses of AL neurons (Fig. 7). 6. In one AL neuron, bicuculline methiodide (BMI) blocked the IPSP produced by electrical stimulation of the antennal nerve, but it did not reduce the inhibitory response to application of ACh (Fig. 8).     

Localization and Distribution of the ATPase Activity and of the Passage of Material Transport in Spike-Stalk and Their Relations to the Development of Spikelets in Wheat

1. The ATPase activity in the spike-stalk cells of wheat was obviously localized at plasmallemma and the surface of cell wall bordering the intercellular spaces and their inclusions. The reactions of ATPase activity at chromatin and nucleoli were usually insignificant, and they were not found in vacuoles and other organelles (Figs. 1, 2, 3, 5, 6 and 7). 2. Three significant differences were observed between the middle part and the basal and upper part of the spike-stalk in wheat. (1) A large amount of inclusions were shown in the intercellular spaces of the middle part, and the high ATPase activity was seen at these inclusions (Figs. 6 and 7), but both they were seldom to be found in the intercellular spaces of the basal and upper part (Figs. 2 and 3). (2) The plasmodesmata of the middle part ceils was more than that of the basal and upper part ones (Figs. 1, 3 and 5). (3) In the middle part cells of spike-stalk, the cytoplasmic material was vigorously and actively transferred through the wall pores, and at the same time, the high ATPase activity was exhibited on the transferred cytoplasm (Figs. 4, 8 and 9). In addition, it was also observed that the cytoplasmic material entered into intercellular spaces from adjacent cells (Fig. 6). But it was hardly to see this phenomenon in the basal and upper part of spike-stalk. 3. It was discussed that the ATPase activity and the passage for material transport may play the role in transferring materials into the spike and they might be related to the development of the wheat spikelets.     

Cytoplasmic intermediate filament proteins and the nuclear lamins A, B and C share the IFA epitope

The murine monoclonal antibody IFA isolated by Pruss et al. (Cell 27 (1981) 419) reacts with all major proteins of the cytoplasmic intermediate filament family (IF) albeit with different affinities but leaves the nucleus undecorated in standard immunofluorescence microscopy. Here we show that IFA reacts with all three nuclear lamins from rat and man in immunoblotting. This is most easily demonstrated in a cell line in which most cells lack cytoplasmic IFs. Thus the rather minor but ubiquitous 66 kD polypeptides identified by Pruss et al. as IF-associated proteins reflect the lamin triplet. While surprising at first, these results are in agreement with the approximate location of the IFA epitope on IF molecules and the recently discovered sequence homology along the rod domain between lamins A and C and IF proteins. Our results extend this relation to lamin B in spite of its unique behaviour during mitosis.     

Genetics of subtilin and nisin biosyntheses

Several peptide antibiotics have been described as potent inhibitors of bacterial growth. With respect to their biosynthesis, they can be devided into two classes: (i) those that are synthesized by a non-ribosomal mechanism and (ii) those that are ribosomally synthesized. Subtilin and nisin belong to the ribosomally synthesized peptide antibiotics. They contain the rare amino acids dehydroalanine, dehydrobutyrine, meso-lanthionine, and 3-methyl-lanthionine. They are derived from prepeptides which are post-translationally modiffied and have been termed lantibiotics because of their characteristic lanthionine bridges (Schnell et al. 1988). Nisin is the most prominent lantibiotic and is used as a food preservative due to its high potency against certain gram-positive bacteria (Mattick & Hirsch 1944, 1947; Rayman & Hurst 1984). It is produced by Lactococcus lactis strains belonging to serological group N. The potent bactericidal activities of nisin and other lantibiotics are based on depolarization of energized bacterial cytoplasmic membranes. Breakdown of the membrane potential is initiated by the formation of pores through which molecules of low molecular weight are released. A trans-negative membrane potential of 50 to 100 mV is necessary for pore formation by nisin (Ruhr & Sahl 1985; Sahl et al. 1987). Nisin occurs as a partially amphiphilic molecule (Van de Ven et al. 1991). Apart from the detergent-like effect of nisin on cytoplasmic membranes, an inhibition of murein synthesis has also been discussed as the primary effect (Reisinger et al. 1980). In several countries nisin is used to prevent the growth of clostridia in cheese and canned food. The nisin peptide structure was first described by Gross & Morall (1971), and its structural gene was isolated in 1988 (Buchman et al. 1988; Kaletta & Entian 1989). Nisin has two natural variants, nisin A and nisin Z, which differ in a single amino acid residue at position 27 (histidin in nisin A is replaced by asparagin in nisin Z (Mulders et al. 1991; De Vos et al. 1993). Subtilin is produced by Bacillus subtilis ATCC 6633. Its chemical structure was first unravelled by Gross & Kiltz (1973) and its structural gene was isolated in 1988 (Banerjee & Hansen 1988). Subtilin shares strong similarities to nisin with an identical organization of the lanthionine ring structures (Fig. 1), and both lantibiotics possess similar antibiotic activities. Due to its easy genetic analysis B. subtilis became a very suitable model organism for the identification and characterization of genes and proteins involved in lantibiotic biosynthesis. The pathway by which nisin is produced is very similar to that of subtilin, and the proteins involved share significant homologies over the entire proteins (for review see also De Vos et al. 1995b). The respective genes have been identified adjacent to the structural genes, and are organized in operon-like structures (Fig. 2). These genes are responsible for post-translational modification, transport of the modified prepeptide, proteolytic cleavage, and immunity which prevents toxic effects on the producing bacterium. In addition to this, biosynthesis of subtilin and nisin is strongly regulated by a two-component regulatory system which consists of a histidin kinase and a response regulator protein.     

Relative Contribution of the Cell Wall, Cytoplasmic Membrane, and Cytoplasm to the Gram-Positive Characteristic of Bacillus megaterium.

Bartholomew, J. W. (University of Southern California, Los Angeles), and Thomas Cromwell. Relative contribution of the cell wall, cytoplasmic membrane, and cytoplasm to the gram-positive characteristic of Bacillus megaterium. J. Bacteriol. 90:643-647. 1965.-A comparison of the roles of the cell wall, cytoplasmic membrane, and cytoplasmic components revealed that the intact cell wall was the dominant contributor to the gram-positive state. Protoplasts of Bacillus megaterium were confirmed as being gram-negative, as reported by Gerhardt et al. The "gram-positive protoplast" report of Amano et al. was shown to be a laboratory-produced artifact, resulting from the comparison of smears made from saline suspensions of Escherichia coli cells with smears made from formalin-sucrose suspensions of B. megaterium protoplasts.