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Spore Formation (spore + formation)
Selected AbstractsResting spore formation of aphid-pathogenic fungus Pandora nouryi depends on the concentration of infective inoculumENVIRONMENTAL MICROBIOLOGY, Issue 7 2008Zhi-Hong Huang Summary Resting spore formation of some aphid-pathogenic Entomophthorales is important for the seasonal pattern of their prevalence and survival but this process is poorly understood. To explore the possible mechanism involved in the process, Pandora nouryi (obligate aphid pathogen) interacted with green peach aphid Myzus persicae on cabbage leaves under favourable conditions. Host nymphs showered with primary conidia of an isolate (LC50: 0.9,6.7 conidia mm,2 4,7 days post shower) from air captures in the low-latitude plateau of China produced resting spores (azygospores), primary conidia or both spore types. Surprisingly, the proportion of mycosed cadavers forming resting spores (Pcfrs) increased sharply within the concentrations (C) of 28,240 conidia mm,2, retained high levels at 240,1760, but was zero or extremely low at 0.3,16. The Pcfrs,C relationship fit well the logistic equation Pcfrs = 0.6774/[1 + exp(3.1229,0.0270C)] (r2 = 0.975). This clarified for the first time the dependence of in vivo resting spore formation of P. nouryi upon the concentration of infective inoculum. A hypothesis is thus proposed that some sort of biochemical signals may exist in the host,pathogen interaction so that the fungal pathogen perceives the signals for prompt response to forthcoming host-density changes by either producing conidia for infecting available hosts or forming resting spores for surviving host absence in situ. [source] Construction and characterization of Bacillus subtilis deletion mutants lacking the prophage 2 - trnS regionFEMS MICROBIOLOGY LETTERS, Issue 2 2006Genki Akanuma Abstract During development of a novel method for constructing a series of deletions in Bacillus subtilis using an isogenic set of gene-disrupted mutants created by integration of pMutin, deletion of the trnS operon, consisting of seven tRNA genes, was found to affect cell growth, development of competence and spore formation. A suppressor (sts1) of the ,trnS mutant was isolated, sequenced and found to have undergone a single base change, CAG to GAG, in the first anticodon of tRNALeu, in the trnB operon. [source] Indole as an intercellular signal in microbial communitiesFEMS MICROBIOLOGY REVIEWS, Issue 4 2010Jin-Hyung Lee Abstract Bacteria can utilize signal molecules to coordinate their behavior to survive in dynamic multispecies communities. Indole is widespread in the natural environment, as a variety of both Gram-positive and Gram-negative bacteria (to date, 85 species) produce large quantities of indole. Although it has been known for over 100 years that many bacteria produce indole, the real biological roles of this molecule are only now beginning to be unveiled. As an intercellular signal molecule, indole controls diverse aspects of bacterial physiology, such as spore formation, plasmid stability, drug resistance, biofilm formation, and virulence in indole-producing bacteria. In contrast, many non-indole-producing bacteria, plants and animals produce diverse oxygenases which may interfere with indole signaling. It appears indole plays an important role in bacterial physiology, ecological balance, and possibly human health. Here we discuss our current knowledge and perspectives on indole signaling. [source] Glucose induction pathway regulates meiosis in Saccharomyces cerevisiae in part by controlling turnover of Ime2p meiotic kinaseFEMS YEAST RESEARCH, Issue 5 2008Misa Gray Abstract Several components of the glucose induction pathway, namely the Snf3p glucose sensor and the Rgt1p and Mth1p transcription factors, were shown to be involved in inhibition of sporulation by glucose. The glucose sensors had only a minor role in regulating transcript levels of the two key regulators of meiotic initiation, the Ime1p transcription factor and the Ime2p kinase, but a major role in regulating Ime2p stability. Interestingly, Rgt1p was involved in glucose inhibition of spore formation but not inhibition of Ime2p stability. Thus, the glucose induction pathway may regulate meiosis through both RGT1- dependent and RGT1- independent pathways. [source] The formation of spores in biofilms of Anoxybacillus flavithermusJOURNAL OF APPLIED MICROBIOLOGY, Issue 3 2009S.A. Burgess Abstract Aims:, To examine the rate and the extent of spore formation in Anoxybacillus flavithermus biofilms and to test the effect of one key variable , temperature , on spore formation. Methods and Results:, A continuous flow laboratory reactor was used to grow biofilms of the typical dairy thermophile A. flavithermus (strain CM) in skim milk. The reactor was inoculated with either a washed culture or a spore suspension of A. flavithermus CM, and was run over an 8·5 h period at three different temperatures of 48, 55 and 60°C. Change in impedance was used to determine the cell numbers in the milk and on the surface of the stainless steel reactor tubes. The biofilm developed at all three temperatures within 6,8 h. Spores formed at 55 and 60°C and amounted to approx. 10,50% of the biofilm. No spores formed at 48°C. Conclusions:, The results suggest that both biofilm formation and spore formation of A. flavithermus can occur very rapidly and simultaneously. In addition, temperature variation has a considerable effect on the formation of spores. Significance and Impact of the Study:, This information will provide direction for developing improved ways in which to manipulate conditions in milk powder manufacturing plants to control biofilms and spores of A. flavithermus. [source] Temporal separation of distinct differentiation pathways by a dual specificity Rap-Phr system in Bacillus subtilisMOLECULAR MICROBIOLOGY, Issue 1 2007Wiep Klaas Smits Summary In bacterial differentiation, mechanisms have evolved to limit cells to a single developmental pathway. The establishment of genetic competence in Bacillus subtilis is controlled by a complex regulatory circuit that is highly interconnected with the developmental pathway for spore formation, and the two pathways appear to be mutually exclusive. Here we show by in vitro and in vivo analyses that a member of the Rap family of proteins, RapH, is activated directly by the late competence transcription factor ComK, and is capable of inhibiting both competence and sporulation. Importantly, RapH is the first member of the Rap family that demonstrates dual specificity, by dephosphorylating the Spo0F,P response regulator and inhibiting the DNA-binding activity of ComA. The protein thus acts at the stage where competence is well initiated, and prevents initiation of sporulation in competent cells as well as contributing to the escape from the competent state. A deletion of rapH induces both differentiation pathways and interferes with their temporal separation. Together, these results indicate that RapH is an integral part of a multifactorial regulatory circuit affecting the cell's decision between distinct developmental pathways. [source] Microarray analysis and functional tests suggest the involvement of expansins in the early stages of symbiosis of the arbuscular mycorrhizal fungus Glomus intraradices on tomato (Solanum lycopersicum)MOLECULAR PLANT PATHOLOGY, Issue 1 2010VLADIMIR DERMATSEV SUMMARY Arbuscular mycorrhizal (AM) symbiosis occurs between fungi of the phylum Glomeromycota and most terrestrial plants. However, little is known about the molecular symbiotic signalling between AM fungi (AMFs) and non-leguminous plant species. We sought to further elucidate the molecular events occurring in tomato, a non-leguminous host plant, during the early, pre-symbiotic stage of AM symbiosis, i.e. immediately before and after contact between the AMF (Glomus intraradices) and the host. We adopted a semi-synchronized AMF root infection protocol, followed by genomic-scale, microarray-based, gene expression profiling at several defined time points during pre-symbiotic AM stages. The microarray results suggested differences in the number of differentially expressed genes and in the differential regulation of several functional groups of genes at the different time points examined. The microarray results were validated and one of the genes induced during contact between AMF and tomato, the expansin-like EXLB1, was functionally analysed. Expansins, encoded by a large multigene family, facilitate plant cell expansion. However, no biological or biochemical function has yet been established for plant-originated expansin-like proteins. EXLB1 transcripts were localized early during the association to cells that may perceive the fungal signal, and later during the association in close proximity to sites of AMF hypha,root colonization. Moreover, in transgenic roots, we demonstrated that a reduction in the steady-state level of EXLB1 transcript was correlated with a reduced rate of infection, reduced arbuscule expansion and reduced AMF spore formation. 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