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Archives of Microbiology (v.195, #4)
Proteomic analysis of conidia germination in Colletotrichum acutatum by Mohamed Rabie El-Akhal; Thomas Colby; Jesús M. Cantoral; Anne Harzen; Jürgen Schmidt; Francisco Javier Fernández-Acero (pp. 227-246).
Colletotrichum acutatum is an important phytopathogenic fungus causing anthracnose in commercially important fruit crops, such as strawberry. The conidia produced by the fungus are survival structures which play a key role in host infection and fungal propagation. Despite its relevance to the fungal life cycle, conidial biology has not been extensively investigated. Here, we provide the first proteomic description of the conidial germination in C. acutatum by comparing the proteomic profiles of ungerminated and germinated conidia. Using two-dimensional electrophoresis combined with MALDI-TOF/TOF mass spectrometry, we have identified 365 proteins in 354 spots, which represent 245 unique proteins, including some proteins with key functions in pathogenesis. All these proteins have been classified according to their molecular function and their involvement in biological processes, including cellular energy production, oxidative metabolism, stress, fatty acid synthesis, protein synthesis, and folding. This report constitutes the first comprehensive study of protein expression during the early stage of the C. acutatum conidial germination. It advances our understanding of the molecular mechanisms involved in the conidial germination process, and provides a useful basis for the further characterization of proteins involved in fungal biology and fungus life cycles.
Keywords: Colletotrichum acutatum ; Conidia germination; MALDI-TOF/TOF MS; Proteomic analysis; Two-dimensional gel electrophoresis
Paenibacillus profundus sp. nov., a deep sediment bacterium that produces isocoumarin and peptide antibiotics by Lyudmila A. Romanenko; Naoto Tanaka; Vassilii I. Svetashev; Natalia I. Kalinovskaya (pp. 247-254).
A novel bacterial strain Sl 79T was isolated from a deep surface sediment sample obtained from the Sea of Japan and investigated by phenotypic and molecular methods. The bacterium Sl 79T was Gram-positive, facultatively anaerobic, spore-forming, motile and able to form two different types of colonies. It contained the major menaquinone MK-7 and anteiso-C15:0 followed by iso-C15:0 as predominant fatty acids. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain Sl 79T belonged to the genus Paenibacillus where it clustered to Paenibacillus apiarius NRRL NRS-1438T with a sequence similarity of 97.7 % and sharing sequence similarities below than 96.7 % to other validly named Paenibacillus species. Strain Sl 79T was found to possess a remarkable inhibitory activity against indicatory microorganisms. On the basis of combined spectral analyses, strain Paenibacillus sp. Sl 79T was established to produce isocoumarin and novel peptide antibiotics. On the basis of DNA–DNA relatedness, phenotypic and phylogenetic data obtained, it was concluded that strain Sl 79T represents a novel species, Paenibacillus profundus sp. nov. with the type strain Sl 79T = KMM 9420T = NRIC 0885T.
Keywords: Paenibacillus profundus sp. nov.; Phylogeny; Antimicrobials; Deep sediments
Phenotype profiling of Rhizobium leguminosarum bv. trifolii clover nodule isolates reveal their both versatile and specialized metabolic capabilities by Andrzej Mazur; Grażyna Stasiak; Jerzy Wielbo; Piotr Koper; Agnieszka Kubik-Komar; Anna Skorupska (pp. 255-267).
Rhizobium leguminosarum bv. trifolii (Rlt) are soil bacteria inducing nodules on clover, where they fix nitrogen. Genome organization analyses of 22 Rlt clover nodule isolates showed that they contained 3–6 plasmids and majority of them possessed large (>1 Mb), chromid-like replicon with exception of four Rlt strains. The Biolog phenotypic profiling comprising utilization of C, N, P, and S sources and tolerance to osmolytes and pH revealed metabolic versatility of the Rlt strains. Statistical analyses of our results showed a clear bias toward specific metabolic preferences, tolerance to unfavorable osmotic conditions, and increased nodulation activity of the strains having smaller amount of extrachromosomal DNA. The K5.4 and K4.15 lacking a large megaplasmid possessed substantially diverse metabolism and belonged to effective clover inoculants. In conclusion, besides overall metabolic versatility, some metabolic specialization may enable rhizobia to persist in variable environments and to compete successfully with other bacteria.
Keywords: Rhizobium leguminosarum ; Biolog metabolic profiling; Symbiosis
Regulated expression systems for the development of whole-cell biocatalysts expressing oxidative enzymes in a sequential manner by Patrizia Di Gennaro; Linda Veronique Kazandjian; Francesco Mezzetti; Guido Sello (pp. 269-278).
This work reports the preparation of two recombinant strains each containing two enzymatic activities mutually expressed through regulated systems for production of functionalized epoxides in one-pot reactions. One strain was Pseudomonas putida PaW340, containing the gene coding for styrene monooxygenase (SMO) from Pseudomonas fluorescens ST under the auto-inducing Ptou promoter and the TouR regulator of Pseudomonas sp. OX1 and the gene coding for naphthalene dihydrodiol dehydrogenase (NDDH) from P. fluorescens N3 under the Ptac promoter inducible by IPTG. The second strain was Escherichia coli JM109, in which the expression of SMO was under the control of the Pnah promoter and the NahR regulator of P. fluorescens N3 inducible by salicylate, while the gene expressing NDDH was under the control of the Plac promoter inducible by IPTG. SMO and NDDH activities were tested in bioconversion experiments using cinnamyl alcohol as reference substrate. The application that we selected is one example of the sequential use of the two enzymatic activities which require a temporal control of the expression of both genes.
Keywords: Regulated expression systems; Pseudomonas ; Oxidative enzymes; Multi-enzymatic reactions; Recombinant strains
Could DNA uptake be a side effect of bacterial adhesion and twitching motility? by M. Bakkali (pp. 279-289).
DNA acquisition promotes the spread of resistance to antibiotics and virulence among bacteria. It is also linked to several natural phenomena including recombination, genome dynamics, adaptation and speciation. Horizontal DNA transfer between bacteria occurs via conjugation, transduction or competence for natural transformation by DNA uptake. Among these, competence is the only mechanism of transformation initiated and entirely controlled by the chromosome of the recipient bacteria. While the molecular mechanisms allowing the uptake of extracellular DNA are increasingly characterized, the function of competence for natural transformation by DNA uptake, the selective advantage maintaining it and the reasons why bacteria take up DNA in the first place are still debated. In this synthesis, I review some of the literature and discuss the four hypotheses on how and why do bacteria take up DNA. I argue that DNA uptake by bacteria is an accidental by-product of bacterial adhesion and twitching motility. Adhesion and motility are generally increased in stressful conditions, which may explain why bacteria increase DNA uptake in these conditions. In addition to its fundamental scientific relevance, the new hypothesis suggested here has significant clinical implications and finds further support from the fact that antibiotics sometimes fail to eliminate the targeted bacterium while inevitably causing stress to others. The widespread misuse of antibiotics may thus not only be selecting for resistant strains, but may also be causing bacteria to take up more DNA with the consequent increase in the chances of acquiring drug resistance and virulence—a scenario in full concordance with the previously reported induction of competence genes by antibiotics in Streptococcus pneumoniae and Legionella pneumophila.
Keywords: Competence; DNA uptake; Transformation; Horizontal gene transfer; Type IV pilus; Twitching motility; Social gliding; Swarming; Bacteria
Characterization of burden on growth due to the nutritional state of media and pre-induced gene expression by Pushkar Malakar; K. V. Venkatesh (pp. 291-295).
Studies have shown that the production of unnecessary proteins burdens the cellular growth mainly due to allocation of cellular resources to unnecessary protein synthesis, thereby limiting the resources available for growth. In the current study, we focus on the effect of pre-induction and nutritional status of the medium on the burden imposed on growth due to the synthesis of unnecessary protein. Escherichia coli cells with different history were grown in a glycerol media with and without IPTG to characterize the burden imposed due to the synthesis of β-galactosidase. Effect of pre-induced lac operon on growth and β-galactosidase expression on lactose milieu was also investigated. The study demonstrates that pre-induction has a strong influence on the extent of burden and is sustained in several generations. Further, the burden was much lower in a rich media relative to that observed in a minimal media.
Keywords: Pre-induced gene expression; Burden on growth; Nutritional content; Unnecessary protein; Escherichia coli ; IPTG