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Sascha L. Hallett Peter J. O'Donoghue Robert J. G. Lester 《The Journal of eukaryotic microbiology》1998,45(1):142-150
ABSTRACT This is the first ultrastructural study of the development of a marine actinosporean and of a species belonging to the genus Sphaeractinomyxon Caullery & Mesnil, 1904. S. ersei n. sp. is described from a limnodriloidine oligochaete, Doliodrilus diverticulatus Erséus, 1985, from Moreton Bay. Queensland, Australia. Development is asynchronous, there being all stages from two-celled pansporoblasts through to mature spores present simultaneously within a host. Spores develop in groups of eight within pansporoblasts in the coelom and when mature are located also in the intestinal lumen. The primordial spore envelope and sporoplasm develop separately in the pansporoblast until the polar filament is formed within the polar capsule and the capsulogenic cell cytoplasm has begun to degrade. The sporoplasm then enters the spore through a separated valve junction. Mature spores are triradially symmetrical with three centrally located polar capsules and a single binucleate sporoplasm with about 46 germ cells. Swellings or projections of the epispore do not occur when spores exit the host and contact sea water. 相似文献
764.
Lichenysins are surface-active lipopeptides with antibiotic properties produced nonribosomally by several strains of Bacillus licheniformis. Here, we report the cloning and sequencing of an entire 26.6-kb lichenysin biosynthesis operon from B. licheniformis ATCC 10716. Three large open reading frames coding for peptide synthetases, designated licA, licB (three modules each), and licC (one module), could be detected, followed by a gene, licTE, coding for a thioesterase-like protein. The domain structure of the seven identified modules, which resembles that of the surfactin synthetases SrfA-A to -C, showed two epimerization domains attached to the third and sixth modules. The substrate specificity of the first, fifth, and seventh recombinant adenylation domains of LicA to -C (cloned and expressed in Escherichia coli) was determined to be Gln, Asp, and Ile (with minor Val and Leu substitutions), respectively. Therefore, we suppose that the identified biosynthesis operon is responsible for the production of a lichenysin variant with the primary amino acid sequence l-Gln–l-Leu–d-Leu–l-Val–l-Asp–d-Leu–l-Ile, with minor Leu and Val substitutions at the seventh position.Many strains of Bacillus are known to produce lipopeptides with remarkable surface-active properties (11). The most prominent of these powerful lipopeptides is surfactin from Bacillus subtilis (1). Surfactin is an acylated cyclic heptapeptide that reduces the surface tension of water from 72 to 27 mN m−1 even in a concentration below 0.05% and shows some antibacterial and antifungal activities (1). Some B. subtilis strains are also known to produce other, structurally related lipoheptapeptides (Table (Table1),1), like iturin (32, 34) and bacillomycin (3, 27, 30), or the lipodecapeptides fengycin (50) and plipastatin (29).
Open in a separate windowaFA, β-hydroxy fatty acid. The β-hydroxy group forms an ester bond with the carboxy group of the C-terminal amino acid. bFA, β-hydroxy fatty acid. The β-hydroxy group forms an ester bond with the carboxy group of Asp5. cFA, β-amino fatty acid. The β-amino group forms a peptide bond with the carboxy group of the C-terminal amino acid. dOnly the following combinations of amino acid 1 and 5 are allowed: Gln-Asp or Glu-Asn. eWhere an alternative amino acid may be present in a structure, the alternative is also presented. In addition to B. subtilis, several strains of Bacillus licheniformis have been described as producing the lipopeptide lichenysin (14, 17, 23, 26, 51). Lichenysins can be grouped under the general sequence l-Glx–l-Leu–d-Leu–l-Val–l-Asx–d-Leu–l-Ile/Leu/Val (Table (Table1).1). The first amino acid is connected to a β-hydroxyl fatty acid, and the carboxy-terminal amino acid forms a lactone ring to the β-OH group of the lipophilic part of the molecule. In contrast to the lipopeptide surfactin, lichenysins seem to be synthesized during growth under aerobic and anaerobic conditions (16, 51). The isolation of lichenysins from cells growing on liquid mineral salt medium on glucose or sucrose basic has been studied intensively. Antimicrobial properties and the ability to reduce the surface tension of water have also been described (14, 17, 26, 51). The structural elucidation of the compounds revealed slight differences, depending on the producer strain. Various distributions of branched and linear fatty acid moieties of diverse lengths and amino acid variations in three defined positions have been identified (Table (Table11).In contrast to the well-defined methods for isolation and structural characterization of lichenysins, little is known about the biosynthetic mechanisms of lichenysin production. The structural similarity of lichenysins and surfactin suggests that the peptide moiety is produced nonribosomally by multifunctional peptide synthetases (7, 13, 25, 49, 53). Peptide synthetases from bacterial and fungal sources describe an alternative route in peptide bond formation in addition to the ubiquitous ribosomal pathway. Here, large multienzyme complexes affect the ordered recognition, activation, and linking of amino acids by utilizing the thiotemplate mechanism (19, 24, 25). According to this model, peptide synthetases activate their substrate amino acids as aminoacyl adenylates by ATP hydrolysis. These unstable intermediates are subsequently transferred to a covalently enzyme-bound 4′-phosphopantetheinyl cofactor as thioesters. The thioesterified amino acids are then integrated into the peptide product through a stepwise elongation by a series of transpeptidations directed from the amino terminals to the carboxy terminals. Peptide synthetases have not only awakened interest because of their mechanistic features; many of the nonribosomally processed peptide products also possess important biological and medical properties.In this report we describe the identification and characterization of a putative lichenysin biosynthesis operon from B. licheniformis ATCC 10716. Cloning and sequencing of the entire lic operon (26.6 kb) revealed three genes, licA, licB, and licC, with structural patterns common to peptide synthetases and a gene designated licTE, which codes for a putative thioesterase. The modular organization of the sequenced genes resembles the requirements for the biosynthesis of the heptapeptide lichenysin. Based on the arrangement of the seven identified modules and the tested substrate specificities, we propose that the identified genes are involved in the nonribosomal synthesis of the portion of the lichenysin peptide with the primary sequence l-Gln–l-Leu–d-Leu–l-Val–l-Asp–d-Leu–l-Ile (with minor Val and Leu substitutions). 相似文献
TABLE 1
Lipoheptapeptide antibiotics of Bacillus spp.Lipopeptide | Organism | Structure | Reference |
---|---|---|---|
Lichenysin A | B. licheniformis | FAa-L-Glu-L-Leu-D-Leu-L-Val-L-Asn-D-Leu-L-Ile | 51, 52 |
Lichenysin B | FAa-L-Glu-L-Leu-D-Leu-L-Val-L-Asp-D-Leu-L-Leu | 23, 26 | |
Lichenysin C | FAa-L-Glu-L-Leu-D-Leu-L-Val-L-Asp-D-Leu-L-Ile | 17 | |
Lichenysin D | FAa-L-Gln-L-Leu-D-Leu-L-Val-L-Asp-D-Leu-L-Ile | This work | |
Surfactant 86 | B. licheniformis | FAa-L-Glxd-L-Leu-D-Leu-L-Val-L-Asxd-D-Leu-L-Ilee | 14, 15 |
L-Val | |||
Surfactin | B. subtilis | FAa-L-Glu-L-Leu-D-Leu-L-Val-L-Asp-D-Leu-L-Leu | 1, 7, 49 |
Esperin | B. subtilis | FAb-L-Glu-L-Leu-D-Leu-L-Val-L-Asp-D-Leu-L-Leue | 45 |
L-Val | |||
Iturin A | B. subtilis | FAc-L-Asn-D-Tyr-D-Asn-L-Gln-L-Pro-D-Asn-L-Ser | 32 |
Iturin C | FAc-L-Asn-D-Tyr-D-Asn-L-Gln-L-Pro-D-Asne-L-Asne | 34 | |
D-Ser-L-Thr | |||
Bacillomycin L | B. subtilis | FAc-L-Asp-D-Tyr-D-Asn-L-Ser-L-Gln-D-Proe-L-Thr | 3 |
D-Ser- | |||
Bacillomycin D | FAc-L-Asp-D-Tyr-D-Asn-L-Pro-L-Glu-D-Ser-L-Thr | 30, 31 | |
Bacillomycin F | FAc-L-Asn-D-Tyr-D-Asn-L-Gln-L-Pro-D-Asn-L-Thr | 27 |
765.
Johanna S. Rehfeld Louis M. Kuhnke Christian Ude Gernot T. John Sascha Beutel 《Engineering in Life Science》2023,23(9):e2300204
In the field of bioprocess development miniaturization, parallelization and flexibility play a key role reducing costs and time. To precisely meet these requirements, additive manufacturing (3D-printing) is an ideal technology. 3D-printing enables rapid prototyping and cost-effective fabrication of individually designed devices with complex geometries on demand. For successful bioprocess development, monitoring of process-relevant parameters, such as pH, dissolved oxygen (DO), and biomass, is crucial. Online monitoring is preferred as offline sampling is time-consuming and leads to loss of information. In this study, 3D-printed cultivation vessels with optical prisms are evaluated for the use in upstream processes of different industrially relevant microorganisms and cell lines. It was shown, that the 3D-printed optically modified well (OMW) is of benefit for a wide range of biotechnologically relevant microorganisms and even for mammalian suspension cells. Evaluation tests with Escherichia coli, Bacillus subtilis, Saccharomyces cerevisiae, and Chinese hamster ovary (CHO) cells were performed, providing highly reproducible results. Growth behavior of OMW cultures was comparable to behavior of shake flask (SF) cultivations and the signal to noise ratio in online biomass measurement was shown to be reduced up to 95.8% by using the OMW. Especially the cultivation phases with low turbidity respective optical densities below 1.0 rel.AU could be monitored accurately for the first time. Furthermore, it was demonstrated that the 3D-printed optics are transferable to different well geometries and sizes, enabling efficient biomass monitoring for individual requirements with tailor-made 3D-printed cultivation vessels in small scale. 相似文献
766.
767.
768.
Regine Claßen-Bockhoff Thomas Speck Enik Tweraser Petra Wester Sascha Thimm Martin Reith 《Organisms Diversity & Evolution》2004,4(3):189-205
Floral key innovations play a significant role in the discussion of adaptive radiation in plants. The paper brings together a brief review of morphological key innovations in plants, elucidating their evolutionary significance in flower–pollinator interactions, and new data on Salvia, a genus being examined as an example for presumed adaptive radiation. We hypothesize that the characteristic staminal lever mechanism functions as a key innovation. It is defined as a functional unit including the modification of stamens to lever-like structures, their reversible movement, and the organization of the remaining floral structures involved in the process of pollen transfer. We follow the assumption that structure and functioning of the staminal levers play a major role in the process of pollen deposition on the pollinator's body, and that minute changes of both their proportions and their interactions with pollinators may have significant consequences for the pollination system. The functioning of the staminal lever mechanism is tested by field investigations, biomechanical experiments and pollination simulations. First results are presented, and possible modes of allopatric and sympatric speciation are discussed, based on morphometry of Salvia flowers and pollinators as well as on the operating mode of the staminal lever mechanism. Special attention is given to species-specific patterns of pollen deposition on the pollinator's body. We assume that, depending on the precision of the lever movement, sympatric Salvia species flowering during overlapping periods and sharing the same pollinating species may be either mechanically isolated from each other or able to hybridize. The latter may result in speciation, as may spontaneous mutations influencing the flower-pollinator interaction, e.g. by significant changes in morphometry of the staminal lever system and/or other flower structures. As a consequence, Salvia individuals may deposit pollen on a different part of the pollinator's body, or even adapt to a new pollinator species, both resulting in reproductive isolation from the parental population. 相似文献
769.
Synaptotagmin-1 utilizes membrane bending and SNARE binding to drive fusion pore expansion 总被引:1,自引:0,他引:1 下载免费PDF全文
Lynch KL Gerona RR Kielar DM Martens S McMahon HT Martin TF 《Molecular biology of the cell》2008,19(12):5093-5103
In regulated vesicle exocytosis, SNARE protein complexes drive membrane fusion to connect the vesicle lumen with the extracellular space. The triggering of fusion pore formation by Ca2+ is mediated by specific isoforms of synaptotagmin (Syt), which employ both SNARE complex and membrane binding. Ca2+ also promotes fusion pore expansion and Syts have been implicated in this process but the mechanisms involved are unclear. We determined the role of Ca2+-dependent Syt-effector interactions in fusion pore expansion by expressing Syt-1 mutants selectively altered in Ca2+-dependent SNARE binding or in Ca2+-dependent membrane insertion in PC12 cells that lack vesicle Syts. The release of different-sized fluorescent peptide-EGFP vesicle cargo or the vesicle capture of different-sized external fluorescent probes was used to assess the extent of fusion pore dilation. We found that PC12 cells expressing partial loss-of-function Syt-1 mutants impaired in Ca2+-dependent SNARE binding exhibited reduced fusion pore opening probabilities and reduced fusion pore expansion. Cells with gain-of-function Syt-1 mutants for Ca2+-dependent membrane insertion exhibited normal fusion pore opening probabilities but the fusion pores dilated extensively. The results indicate that Syt-1 uses both Ca2+-dependent membrane insertion and SNARE binding to drive fusion pore expansion. 相似文献
770.
In Drosophila embryos and larvae, a small number of identified motor neurons innervate body wall muscles in a highly stereotyped pattern. Although genetic screens have identified many proteins that are required for axon guidance and synaptogenesis in this system, little is known about the mechanisms by which muscle fibers are defined as targets for specific motor axons. To identify potential target labels, we screened 410 genes encoding cell-surface and secreted proteins, searching for those whose overexpression on all muscle fibers causes motor axons to make targeting errors. Thirty such genes were identified, and a number of these were members of a large gene family encoding proteins whose extracellular domains contain leucine-rich repeat (LRR) sequences, which are protein interaction modules. By manipulating gene expression in muscle 12, we showed that four LRR proteins participate in the selection of this muscle as the appropriate synaptic target for the RP5 motor neuron. 相似文献