Electroactivity of the Gram-positive bacterium Paenibacillus dendritiformis MA-72.

Whilst most of the microorganisms recognized as exoelectrogens are Gram-negative bacteria, the electrogenicity of Gram-positive bacteria has not been sufficiently explored. In this study, the putative electroactivity of the Gram-positive Paenibacillus dendritiformis MA-72 strain, isolated from the anodic biofilm of long-term operated Sediment Microbial Fuel Cell (SMFC), has been investigated. SEM observations show that under polarization conditions P. dendritiformis forms a dense biofilm on carbon felt electrodes. A current density, reaching 5 mA m-2, has been obtained at a prolonged applied potential of -0.195 V (vs. SHE), which represents 35% of the value achieved with the SMFC. The voltammetric studies confirm that the observed Faradaic current is associated with the electrochemical activity of the bacterial biofilm and not with a soluble redox mediator. The results suggest that a direct electron transfer takes place through the conductive extracellular polymer matrix via pili/nanowires and multiple cytochromes. All these findings demonstrate for the first time that the Gram-positive Paenibacillus dendritiformis MA-72 is a new exoelectrogenic bacterial strain.

The coffee-machine bacteriome: biodiversity and colonisation of the wasted coffee tray leach.

Microbial communities are ubiquitous in both natural and artificial environments. However, microbial diversity is usually reduced under strong selection pressures, such as those present in habitats rich in recalcitrant or toxic compounds displaying antimicrobial properties. Caffeine is a natural alkaloid present in coffee, tea and soft drinks with well-known antibacterial properties. Here we present the first systematic analysis of coffee machine-associated bacteria. We sampled the coffee waste reservoir of ten different Nespresso machines and conducted a dynamic monitoring of the colonization process in a new machine. Our results reveal the existence of a varied bacterial community in all the machines sampled, and a rapid colonisation process of the coffee leach. The community developed from a pioneering pool of enterobacteria and other opportunistic taxa to a mature but still highly variable microbiome rich in coffee-adapted bacteria. The bacterial communities described here, for the first time, are potential drivers of biotechnologically relevant processes including decaffeination and bioremediation.

Characterization of a phiBP endolysin encoded by the Paenibacillus polymyxa CCM 7400 phage.

Endolysin (gp1.2) from the Paenibacillus polymyxa CCM 7400 temperate phage phiBP has a modular structure consisting of an N-terminal region with a catalytic glycosyl hydrolase 25 domain and a C-terminal cell wall-binding domain. The entire gene of this endolysin and fragments containing its catalytic and binding domains separately were cloned into expression vectors and the corresponding recombinant proteins were expressed in Escherichia coli and purified by affinity chromatography. The lytic activities of endolysin and its catalytic domain were tested on cell wall substrates from paenibacilli, bacilli, corynebacteria and E. coli. The presence of a cell wall-binding domain was found to be essential, as the phiBP endolysin was fully active only as a full-length protein. The binding ability of the cell wall-binding domain alone and in fusion with green fluorescent protein was demonstrated by specific binding assays to the cell surface of P. polymyxa CCM 7400 and to those of other Paenibacillus strains. Thus the ability of phiBP endolysin to hydrolyze the paenibacilli cell wall was confirmed.

Periodic reversals in Paenibacillus dendritiformis swarming.

Bacterial swarming is a type of motility characterized by a rapid and collective migration of bacteria on surfaces. Most swarming species form densely packed dynamic clusters in the form of whirls and jets, in which hundreds of rod-shaped rigid cells move in circular and straight patterns, respectively. Recent studies have suggested that short-range steric interactions may dominate hydrodynamic interactions and that geometrical factors, such as a cell's aspect ratio, play an important role in bacterial swarming. Typically, the aspect ratio for most swarming species is only up to 5, and a detailed understanding of the role of much larger aspect ratios remains an open challenge. Here we study the dynamics of Paenibacillus dendritiformis C morphotype, a very long, hyperflagellated, straight (rigid), rod-shaped bacterium with an aspect ratio of ~20. We find that instead of swarming in whirls and jets as observed in most species, including the shorter T morphotype of P. dendritiformis, the C morphotype moves in densely packed straight but thin long lines. Within these lines, all bacteria show periodic reversals, with a typical reversal time of 20 s, which is independent of their neighbors, the initial nutrient level, agar rigidity, surfactant addition, humidity level, temperature, nutrient chemotaxis, oxygen level, illumination intensity or gradient, and cell length. The evolutionary advantage of this unique back-and-forth surface translocation remains unclear.

Antimicrobial factor from Bacillus amyloliquefaciens inhibits Paenibacillus larvae, the causative agent of American foulbrood.

Bacillus amyloliquefaciens LBM 5006 produces an antimicrobial factor active against Paenibacillus larvae, a major honeybee pathogen. The antagonistic effect and the mode of action of the antimicrobial factor were investigated. The antibacterial activity was produced starting at mid-logarithmic growth phase, reaching its maximum during the stationary phase. Exposure of cell suspensions of P. larvae to this antimicrobial resulted in loss of cell viability and reduction in optical density associated with cell lysis. Scanning electron microscopy showed damaged cell envelope and loss of protoplasmic material. The antimicrobial factor was stable for up to 80°C, but it was sensitive to proteinase K and trypsin. Mass spectrometry analysis indicates that the antimicrobial activity is associated with iturin-like peptides. The antimicrobial factor from B. amyloliquefaciens LBM 5006 showed a bactericidal effect against P. larvae cells and spores. This is the first report on iturin activity against P. larvae. This antimicrobial presents potential for use in the control of American foulbrood disease.

Mutually facilitated dispersal between the nonmotile fungus Aspergillus fumigatus and the swarming bacterium Paenibacillus vortex.

In the heterogeneous environment surrounding plant roots (the rhizosphere), microorganisms both compete and cooperate. Here, we show that two very different inhabitants of the rhizosphere, the nonmotile fungus Aspergillus fumigatus and the swarming bacterium Paenibacillus vortex, can facilitate each other's dispersal. A. fumigatus conidia (nonmotile asexual fungal spores) can be transported by P. vortex swarms over distances of at least 30 cm and at rates of up to 10.8 mm h(-1). Moreover, conidia can be rescued and transported by P. vortex from niches of adverse growth conditions. Potential benefit to the bacteria may be in crossing otherwise impenetrable barriers in the soil: fungal mycelia seem to act as bridges to allow P. vortex to cross air gaps in agar plates. Transport of conidia was inhibited by proteolytic treatment of conidia or the addition of purified P. vortex flagella, suggesting specific contacts between flagella and proteins on the conidial surface. Conidia were transported by P. vortex into locations where antibiotics inhibited bacteria growth, and therefore, growth and sporulation of A. fumigatus were not limited by bacterial competition. Conidia from other fungi, similar in size to those fungi from A. fumigatus, were not transported as efficiently by P. vortex. Conidia from a range of fungi were not transported by another closely related rhizosphere bacterium, Paenibacillus polymyxa, or the more distantly related Proteus mirabilis, despite both being efficient swarmers.

Paenibacillus telluris sp. nov., a novel phosphate-solubilizing bacterium isolated from soil.

A phosphate-solubilizing bacterial strain designated PS38(T) was isolated from farm soil. The isolate was a Gram-positive, motile, endospore-forming, rod-shaped bacterium. It grew optimally at 37°C and pH 7.5. The predominant cellular fatty acids were anteiso-C(15:0), anteiso-C(17:0), and iso-C(16:0). The DNA G+C content was 49.5 mol% and the predominant menaquinone was MK-7. Phylogenese analyses based on 16S rRNA gene sequences showed that the strain PS38(T) belonged to the genus Paenibacillus and was most closely related to Paenibacillus chibensis JCM 9905(T), P. barengoltzii SAFN-016(T), P. timonensis 2301032(T), and P. motobuensis MC10(T) with 96.3%, 96.0%, 95.9%, and 95.5% 16S rRNA gene sequence similarity, respectively. On the basis of morphological, chemotaxonomic, physiological, and phylogenetic properties, strain PS38(T) represents a novel species of the genus Paenibacillus, for which the name Paenibacillus telluris sp. nov. is proposed. The type strain is PS38(T) (=KCTC 13946(T) =CGMCC 1.10695(T)).

Indole and 3-indolylacetonitrile inhibit spore maturation in Paenibacillus alvei.

BACKGROUND: Bacteria use diverse signaling molecules to ensure the survival of the species in environmental niches. A variety of both gram-positive and gram-negative bacteria produce large quantities of indole that functions as an intercellular signal controlling diverse aspects of bacterial physiology. RESULTS: In this study, we sought a novel role of indole in a gram-positive bacteria Paenibacillus alvei that can produce extracellular indole at a concentration of up to 300 µM in the stationary phase in Luria-Bertani medium. Unlike previous studies, our data show that the production of indole in P. alvei is strictly controlled by catabolite repression since the addition of glucose and glycerol completely turns off the indole production. The addition of exogenous indole markedly inhibits the heat resistance of P. alvei without affecting cell growth. Observation of cell morphology with electron microscopy shows that indole inhibits the development of spore coats and cortex in P. alvei. As a result of the immature spore formation of P. alvei, indole also decreases P. alvei survival when exposed to antibiotics, low pH, and ethanol. Additionally, indole derivatives also influence the heat resistance; for example, a plant auxin, 3-indolylacetonitrile dramatically (2900-fold) decreased the heat resistance of P. alvei, while another auxin 3-indoleacetic acid had a less significant influence on the heat resistance of P. alvei. CONCLUSIONS: Together, our results demonstrate that indole and plant auxin 3-indolylacetonitrile inhibit spore maturation of P. alvei and that 3-indolylacetonitrile presents an opportunity for the control of heat and antimicrobial resistant spores of gram-positive bacteria.

Genome sequence of the pattern forming Paenibacillus vortex bacterium reveals potential for thriving in complex environments.

BACKGROUND: The pattern-forming bacterium Paenibacillus vortex is notable for its advanced social behavior, which is reflected in development of colonies with highly intricate architectures. Prior to this study, only two other Paenibacillus species (Paenibacillus sp. JDR-2 and Paenibacillus larvae) have been sequenced. However, no genomic data is available on the Paenibacillus species with pattern-forming and complex social motility. Here we report the de novo genome sequence of this Gram-positive, soil-dwelling, sporulating bacterium. RESULTS: The complete P. vortex genome was sequenced by a hybrid approach using 454 Life Sciences and Illumina, achieving a total of 289× coverage, with 99.8% sequence identity between the two methods. The sequencing results were validated using a custom designed Agilent microarray expression chip which represented the coding and the non-coding regions. Analysis of the P. vortex genome revealed 6,437 open reading frames (ORFs) and 73 non-coding RNA genes. Comparative genomic analysis with 500 complete bacterial genomes revealed exceptionally high number of two-component system (TCS) genes, transcription factors (TFs), transport and defense related genes. Additionally, we have identified genes involved in the production of antimicrobial compounds and extracellular degrading enzymes. CONCLUSIONS: These findings suggest that P. vortex has advanced faculties to perceive and react to a wide range of signaling molecules and environmental conditions, which could be associated with its ability to reconfigure and replicate complex colony architectures. Additionally, P. vortex is likely to serve as a rich source of genes important for agricultural, medical and industrial applications and it has the potential to advance the study of social microbiology within Gram-positive bacteria.

Cell surface xylanases of the glycoside hydrolase family 10 are essential for xylan utilization by Paenibacillus sp. W-61 as generators of xylo-oligosaccharide inducers for the xylanase genes.

Paenibacillus sp. W-61 is capable of utilizing water-insoluble xylan for carbon and energy sources and has three xylanase genes, xyn1, xyn3, and xyn5. Xyn1, Xyn3, and Xyn5 are extracellular enzymes of the glycoside hydrolase (GH) families 11, 30, and 10, respectively. Xyn5 contains several domains including those of carbohydrate-binding modules (CBMs) similar to a surface-layer homologous (SLH) protein. This study focused on the role of Xyn5, localized on the cell surface, in water-insoluble xylan utilization. Electron microscopy using immunogold staining revealed Xyn5 clusters over the entire cell surface. Xyn5 was bound to cell wall fractions through its SLH domain. A Deltaxyn5 mutant grew poorly and produced minimal amounts of Xyn1 and Xyn3 on water-insoluble xylan. A Xyn5 mutant lacking the SLH domain (Xyn5DeltaSLH) grew poorly, secreting Xyn5DeltaSLH into the medium and producing minimal Xyn1 and Xyn3 on water-insoluble xylan. A mutant with an intact xyn5 produced Xyn5 on the cell surface, grew normally, and actively synthesized Xyn1 and Xyn3 on water-insoluble xylan. Quantitative reverse transcription-PCR showed that xylobiose, generated from water-insoluble xylan decomposition by Xyn5, is the most active inducer for xyn1 and xyn3. Luciferase assays using a Xyn5-luciferase fusion protein suggested that xylotriose is the best inducer for xyn5. The cell surface Xyn5 appears to play two essential roles in water-insoluble xylan utilization: (i) generation of the xylo-oligosaccharide inducers of all the xyn genes from water-insoluble xylan and (ii) attachment of the cells to the substrate so that the generated inducers can be immediately taken up by cells to activate expression of the xyn system.