Phenotypic and phylogenetic studies were performed on two myxobacterial strains, SMP-2 and SMP-10, isolated from coastal regions. The two strains are morphologically similar, in that both produce ...yellow fruiting bodies, comprising several sessile sporangioles in dense packs. They are differentiated from known terrestrial myxobacteria on the basis of salt requirements (2–3% NaCl) and the presence of anteiso-branched fatty acids. Comparative 16S rRNA gene sequencing studies revealed that SMP-2 and SMP-10 are genetically related, and constitute a new cluster within the myxobacteria group, together with the Polyangium vitellinum Pl vt1 strain as the closest neighbor. The sequence similarity between the two strains is 95.6%. Based on phenotypic and phylogenetic evidence, it is proposed that these two strains be assigned to a new genus, Haliangium gen. nov., with SMP-2 designated as Haliangium ochraceum sp. nov. (=JCM 11303T=DSM 14365T), and SMP-10 as Haliangium tepidum sp. nov. (=JCM 11304T=DSM 14436T).
CarD is the only reported prokaryotic protein showing structural and functional features typical of eukaryotic high-mobility group A transcription factors. In prokaryotes, proteins similar to CarD ...appear to be confined primarily to myxobacteria. In Myxococcus xanthus, CarD has been previously shown to act as a positive element in two different regulatory networks: one for light-induced synthesis of carotenoids and the other for starvation-induced fruiting body formation. We have now tested the effect of a loss-of-function mutation in the carD gene (carD1) on the expression of a random collection of lacZ-tagged genes, which are normally expressed in the dark during vegetative growth in rich medium. Our results indicate that CarD plays a significant role in the transcriptional regulation of various indicated genes. The carD1 mutation downregulates some genes and upregulates others. Also reported here is the isolation of several mutations that suppress the strong effect of carD1 on the expression of a particular vegetative gene. One of them (sud-2) also suppresses the effect of carD1 on other vegetative genes and on fruiting-body formation. Thus, CarD and the sud-2 gene product appear to participate in a single mechanism, which underlies various apparently diverse regulatory phenomena ascribed to CarD.
A bacterial artificial chromosome (BAC) library was constructed to isolate the biosynthetic gene cluster for the polyketide/peptide hybrid-type antibiotic cystothiazole A from the myxobacterium ...Cystobacter fuscus strain AJ-13278. Sequence analysis of a 63.9 kb contiguous region that encompasses the biosynthetic gene cluster (eta) led to the identification of a polyketide synthase (PKS)/nonribosomal peptide synthetase (NRPS) hybrid gene cluster 32.1kb in size, which consists of six open reading frames (ORFs), ctaB to ctaG, as well as downstream genes ctaJ and ctaK (1.0 and 0.9 kb, respectively) responsible for the final biosynthetic steps. The genes ctaB, ctaE, and ctaF encode PKSs, the genes ctaC and ctaG encode NRPSs, and ctaD encodes an NRPS-PKS hybrid enzyme. Disruption of ctaD impaired cystothiazole A production. Additionally, two downstream genes, ctaJ and ctaK, which encode a nitrilase and an O-methyltransferase, respectively, must be responsible for the final methyl ester formation in the cystothiazole A biosynthesis.
Soraphinol C, a new free-radical scavenger from Sorangium cellulosum Li, Xuemei (Sungkyunkwan University, Suwon, Republic of Korea); Yu, T.K. (Korea Maritime University, Busan, Republic of Korea); Kwak, J.H. (Sungkyunkwan University, Suwon, Republic of Korea) ...
Journal of microbiology and biotechnology,
03/2008, Letnik:
18, Številka:
3
Journal Article
Recenzirano
A new compound named soraphinol C (1) was isolated from myxobacteria Sorangium cellulosum KM1001 a soil isolate, together with a structurally related known compound, 4-hydroxysattabacin (2). These ...compounds were isolated by silica gel column chromatography and recycling preparative HPLC, consecutively. The structures of the compounds were determined on the basis of combined spectroscopic analyses. Compounds 1 and 2 exhibited antioxidant activity as a radical scavenger in the experiment using a hydrophilic free-radical initiator, 2,2'-azobis(2-amidinopropane)dihydrochloride with ORAC values of 0.956 and 0.617, respectively.
Epothilones, potent cytotoxic agents and potential anticancer drugs, are complex polyketides produced by a modular polyketide synthase (PKS). The epothilone PKS genes were introduced and expressed in ...Myxococcus xanthus and engineered to generate novel unnatural natural products which can be used as new scaffolds for chemical modification. Inactivation of the KR domain in module 6 of the epo PKS resulted in accumulation of 9-oxoepothilone D and its isomer 8-epi-9-oxoepothilone D as the major products. Modification of the KR domain in module 4 resulted in the production of the expected compound 12,13-dihydro-13-oxoepothilone C in trace amounts, and the unexpected compound 11,12-dehydro-12,13-dihydro-13-oxoepothilone D as the major product. The other expected compound, 12,13-dihydro-13-oxoepothilone D, was not detected. The unexpected 13-oxo derivative produced indicates that the ER domain of module 5 has substrate-specificity requirements and suggests a second enzymatic role for the domain.
Various bioactive small molecules produced by microbial cultivation are degraded in the culture broth or may repress the formation of additional product. The inclusion of hydrophobic adsorber resin ...beads to capture these products in situ and remove them from the culture broth can reduce or prevent this degradation and repression. These product capture beads are often subjected to a dynamic and stressful microenvironment for a long cultivation time, affecting their physical structure and performance. Impact and collision forces can result in the fracturing of these beads into smaller pieces, which are difficult to recover at the end of a cultivation run. Various contaminating compounds may also bind in a non-specific manner to these beads, reducing the binding capacity of the resin for the product of interest (fouling). This study characterizes resin bead binding capacity (to monitor bead fouling), and resin bead volume distributions (to monitor bead fracture) for an XAD-16 adsorber resin used to capture epothilone produced during myxobacterial cultivations. Resin fouling was found to reduce the product binding capacity of the adsorber resin by 25-50%. Additionally, the degree of resin bead fracture was found to be dependent on the cultivation length and the impeller rotation rate. Microbial cultivations and harvesting processes should be designed in such a way to minimize bead fragmentation and fouling during cultivation to maximize the amount of resin and associated product harvested at the end of a run.
Operon Required for Fruiting Body Development in Myxococcus xanthus Kim, D.H., Hoseo University, Asan, Republic of Korea; Chung, J.W., Hoseo University, Asan, Republic of Korea; Hyun, H.S., Hoseo University, Asan, Republic of Korea ...
Journal of microbiology and biotechnology,
11/2009, Letnik:
19, Številka:
11
Journal Article
Recenzirano
We have used mutational analysis to identify four genes, MXAN3553, MXAN3554, MXAN3555, and MXAN3556, constituting an operon that is essential for normal fruiting body development in Myxococcus ...xanthus. Deletion of MXAN3553, which encoded a hypothetical protein, resulted in delayed fruiting body development. MXAN3554 was predicted to encode a metallopeptidase, and its deletion caused fruiting body formation to fail. Inactivation of MXAN3555, which encoded a putative NtrC-type response regulator, resulted in delayed aggregation and a severe reduction in sporulation. Fruiting bodies also failed to develop with the deletion of MXAN3556, another gene encoding a hypothetical protein.
A novel macrolide, isolated from the myxobacteria Sorangium cellulosum WXNXJ-C, was identified as 1,7,12,13-tetrahydroxy-14-methoxy-8,10-dimethyl-6-phenyl-5,15-dioxa-bicyclo9.3.1pentadecan-4-one, ...“Phoxalone”. It had minimum IC₅₀ values of 0.24, 6.9, 10.3, 0.98 and 4 μg/ml, respectively, against tumour cell lines: B16, Bel7402, H446, MCF-7, and SGC7901. In addition, it had less cytotoxicity to normal human liver L02 cell lines (286 μg/ml, 24 h). A cytotoxic bioactivity study on H446 cell line in vitro suggested that Phoxalone arrested the mitosis in the G2/M phase.
Dawenol, a New Polyene Metabolite from the Myxobacterium Söker, Udo; Kunze, Brigitte; Reichenbach, Hans ...
Zeitschrift für Naturforschung. B, A journal of chemical sciences,
10/2003, Letnik:
58, Številka:
10
Journal Article
Recenzirano
A group of new polyene metabolites was detected in several crude extracts of the myxobacterium Stigmatella aurantiaca. The main compound dawenol (1) was isolated from cultures of S. aurantiaca, ...strain DW4/3-1. Its n-eicosaheptaene structure was elucidated by spectroscopic methods.
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