In vitro effects of alginate lyase SG4 + produced by Paenibacillus lautus alone and combined with antibiotics on biofilm formation by mucoid Pseudomonas aeruginosa.

Alginate is a major extra polymeric substance in the biofilm formed by mucoid Pseudomonas aeruginosa. It is the main proven perpetrator of lung infections in patients suffering from cystic fibrosis. Alginate lyases are very important in the treatment of cystic fibrosis. This study evaluated the role of standalone and in conjugation, effect of alginate lyase of SG4 + isolated from Paenibacillus lautus in enhancing in vitro bactericidal activity of gentamicin and amikacin on mucoid P. aeruginosa. Using Response Surface Methodology (RSM) alginate lyase SG4 + production was optimized in shake flask and there 8.49-fold enhancement in enzyme production. In fermenter, maximum growth (10.15 mg/ml) and alginate lyase (1.46 International Units) production, 1.71-fold was increased using Central Composite Design (CCD). Further, fermentation time was reduced from 48 to 20 h. To the best of our knowledge this is the first report in which CCD was used for fermenter studies to optimize alginate lyase production. The Km and Vmax of purified enzyme were found to be 2.7 mg/ml and 0.84 mol/ml-min, respectively. The half-life (t 1/2) of purified alginate lyase SG4 + at 37 °C was 180 min. Alginate lyase SG4 + in combination with gentamicin and amikacin eradiated 48.4- 52.3% and 58- 64.6%, alginate biofilm formed by P. aeruginosa strains, respectively. The study proves that alginate lyase SG4 + has excellent exopolysaccharide disintegrating ability and may be useful in development of potent therapeutic agent to treat P. aeruginosa biofilms.

Field-Realistic Tylosin Exposure Impacts Honey Bee Microbiota and Pathogen Susceptibility, Which Is Ameliorated by Native Gut Probiotics.

Antibiotics have been applied to honey bee (Apis mellifera) hives for decades to treat Paenibacillus larvae, which causes American foulbrood disease and kills honey bee larvae. One of the few antibiotics approved in apiculture is tylosin tartrate. This study examined how a realistic hive treatment regimen of tylosin affected the gut microbiota of bees and susceptibility to a bacterial pathogen. Tylosin treatment reduced bacterial species richness and phylogenetic diversity and reduced the absolute abundances and strain diversity of the beneficial core gut bacteria Snodgrassella alvi and Bifidobacterium spp. Bees from hives treated with tylosin died more quickly after being fed a bacterial pathogen (Serratia marcescens) in the laboratory. We then tested whether a probiotic cocktail of core bee gut species could bolster pathogen resistance. Probiotic exposure increased survival of bees from both control and tylosin-treated hives. Finally, we measured tylosin tolerance of core bee gut bacteria by plating cultured isolates on media with different tylosin concentrations. We observed highly variable responses, including large differences among strains of both S. alvi and Gilliamella spp. Thus, probiotic treatments using cultured bee gut bacteria may ameliorate harmful perturbations of the gut microbiota caused by antibiotics or other factors. IMPORTANCE The antibiotic tylosin tartrate is used to treat honey bee hives to control Paenibacillus larvae, the bacterium that causes American foulbrood. We found that bees from tylosin-treated hives had gut microbiomes with depleted overall diversity as well as reduced absolute abundances and strain diversity of the beneficial bee gut bacteria Snodgrassella alvi and Bifidobacterium spp. Furthermore, bees from treated hives suffered higher mortality when challenged with an opportunistic pathogen. Bees receiving a probiotic treatment, consisting of a cocktail of cultured isolates of native bee gut bacteria, had increased survival following pathogen challenge. Thus, probiotic treatment with native gut bacteria may ameliorate negative effects of antibiotic exposure.

Microbial radiosensitization using combined treatments of essential oils and irradiation- part B: Comparison between gamma-ray and X-ray at different dose rates.

Stored rice and rice products are prone to contamination by pathogenic fungi and bacteria such as Aspergillus niger, Bacillus cereus, and Paenibacillus amylolyticus. Treatment with antimicrobial essential oils (EOs) and irradiation are options to control spoilage organisms. Microbial samples with or without fumigation with an oregano/thyme EO mixture were irradiated at 0.5, 0.75, 1.0, 1.5, 2.0, 2.5, 3.0 and 3.5 kGy for calculation of a D10 value. The relative sensitivity was calculated as the ratio of D10 values for the irradiation plus oregano and thyme EO combination and irradiation alone treatments. In all cases, irradiation plus fumigation with the oregano and thyme EO mixture showed increased efficacy compared with irradiation alone. The relative sensitivity of γ-ray irradiation against A. niger was 1.22, 1.33, and 1.24 for radiation dose rates of 10.445, 4.558, and 0.085 kGy/h, respectively, however against B. cereus it was 1.28, 1.45, and 1.49, and against P. amylolyticus it was 1.35, 1.33, and 1.38, for respective γ-ray irradiation dose rates. The relative sensitivity of X-ray irradiation against A. niger, B. cereus, and P. amylolyticus was 1.63, 1.21, and 1.31, respectively, at the X-ray dose rate of 0.76 kGy/h. The results showed that the relative sensitivity of γ-ray irradiation was higher against the two bacteria than the fungus, whereas X-ray showed higher sensitivity against the fungus than the two bacteria. There was no consistent positive or negative relationship between dose rate and relative sensitivity. The results demonstrated the potential of an oregano and thyme EOs mixture as an antimicrobial agent and its efficacy to increase the radiosensitization of A. niger, B. cereus, and P. amylolyticus during γ-ray or X-ray irradiation treatments.

Transcriptome analysis of polysaccharide-based microbial flocculant MBFA9 biosynthesis regulated by nitrogen source.

Microbial flocculant (MBF), an environmentally friendly water treatment agent, can be widely used in various water treatments. However, its use is limited by low yield and high cost. This problem can be solved by clarifying its biosynthesis mechanism and regulating it. Paenibacillus shenyangensis A9, a flocculant-producing bacterium, was used to produce polysaccharide-type MBFA9 by regulating the nitrogen source (nitrogen adequacy/nitrogen deficiency). In this study, RNA-Seq high-throughput sequencing technology and bioinformatic approaches were used to investigate the fermentation and biosynthesis of polysaccharide-type MBFA9 by regulating the nitrogen source (high nitrogen/low nitrogen) in the flocculant-producing bacteria Paenibacillus shenyangensis A9. Differentially expressed genes, functional clustering, and functional annotation of key genes were assessed. Then the MBFA9 biosynthesis and metabolic pathway were reconstructed. Our results showed that when cultured under different nitrogen conditions, bacterial strain A9 had a greater ability to synthesize polysaccharide-type MBFA9 under low nitrogen compared to high nitrogen conditions, with the yield of MBFA9 reaching 4.2 g/L at 36 h of cultivation. The quality of transcriptome sequencing data was reliable, with a matching rate of 85.38% and 85.48% when L36/H36 was mapped to the reference genome. The total expressed genes detected were 4719 and 4730, with 265 differentially expressed genes. The differentially expressed genes were classified into 3 categories: molecular function (MF), cell component (CC), and biological process (BP), and can be further divided into 22 subcategories. There were 192 upregulated genes and 73 downregulated genes, with upregulation being predominant under low nitrogen. UDP-Gal, UDP-Glc, UDP-GlcA, and UDP-GlcNAc, which are in the polysaccharide metabolic pathway, could all be used as precursors for MBFA9 biosynthesis, and murA, wecB, pgm, galU/galF, fcl, gmd, and glgC were the main functional genes capable of affecting the growth of bacteria and the biosynthesis of MBF. Results from this study provide evidence that high-level expression of key genes in MBFA9 biosynthesis, regulation, and control can achieve MBFA9 directional synthesis for large-scale applications.

Potential synergistic antimicrobial efficiency of binary combinations of essential oils against Bacillus cereus and Paenibacillus amylolyticus-Part A.

The checkerboard method was used to study the potential interactions between eight essential oils (Basil, Cinnamon, Eucalyptus, Mandarin, Oregano, Peppermint, Tea tree, and Thyme) when used as antibacterial agents against Bacillus cereus LSPQ 2872 and Paenibacillus amylolyticus ATCC 9995. The minimum inhibitory concentration (MIC) of each essential oil (EO) and the fractional inhibitory concentration (FIC) index for the binary combinations of essential oils (EOs) were determined. According to FIC index values, some of the compound binary combinations showed an additive effect; however, Thyme/Tea tree and Cinnamon/Thyme EOs exhibited a synergistic effect against P. amylolyticus and B. cereus, respectively. Cinnamon/Thyme EOs mixture exhibited no interactive effect against P. amylolyticus, but a synergistic effect against B. cereus. The combination of Oregano/Thyme EOs displayed the best antibacterial activity and showed a synergistic effect against B. cereus and P. amylolyticus bacteria. The Oregano/Thyme EOs mixture has potential application in food preservation to reduce the contamination of B. cereus and P. amylolyticus.

Isolation and characterization of a moderate thermophilic Paenibacillus naphthalenovorans strain 4B1 capable of degrading dibenzofuran from dioxin-contaminated soil in Vietnam.

A moderate thermophilic dibenzofuran (DF) degrader, strain 4B1, was isolated from dioxin-contaminated soil in Vietnam under thermophilic condition. A 16S rRNA gene sequence analysis assigned the strain to genus Paenibacillus. The optimum growth temperature of strain 4B1 was 45°C with a doubling time of 2.7 h in the presence of DF as a sole carbon and energy source. The rate of its growth and DF-degradation were approximately 3-fold higher than those of a reference Paenibacillus sp. strain. The 4B1 strain degraded 89% of 1000 mg L-1 DF within 48 h cultivation at the optimum temperature. TBLASTN analysis based on its draft genome sequence revealed that this strain possessed a dbf gene cluster. The open reading frames (dbfA1A2RBC) in the cluster shared 99-100% identity with those of Paenibacillus sp. YK5, indicating that DF was likely degraded by an angular dioxygenation pathway in strain 4B1. Four genes in the dbf gene cluster (dbfA1A2BC) were partially induced by DF, which was observed by semi-quantitative RT-PCR. Quantitative PCR analysis of dbfA1 transcripts, encoding the alpha subunit of DF dioxygenase, indicated that dbfA1 was expressed 4-times higher than that of strain YK5 at 45°C. These results suggest that the faster growth and degradation of DF in strain 4B1 could be due to differences in transcriptional regulation of dbf cluster genes.

Chlorothalonil tolerance of indole producing bacteria associated to wheat (Triticum turgidum L.) rhizosphere in the Yaqui Valley, Mexico.

Chlorothalonil is a commonly used fungicide to control the karnal bunt caused by Tilletia indica Mitra in wheat production from the Yaqui Valley, Mexico. Here, the effect of Chlorothalonil on the growth of 132 bacterial strains associated with wheat rhizosphere from the Yaqui Valley was evaluated, as well as their ability to produce indoles. Thirty-three percent of the evaluated strains were inhibited by Chlorothalonil, being Bacillus and Paenibacillus the most inhibited genera, observing an inhibition >50% of their strains. In addition, 49% of the inhibited strains showed the ability to produce indoles (>5 µg/mL), where the genus Bacillus was the most abundant (80%). The remaining strains (67%) were tolerant to the evaluated fungicide, but only 37% of those showed the ability to produce indoles, which could be considered as Plant Growth Promoting Rhizobacteria (PGPR). These results showed that Chlorothalonil is not only an antifungal compound but also inhibits the growth of bacterial strains with the ability to produce indoles. Thus, the intensive application of fungicides to agro-systems needs more validation in order to develop sustainable agricultural practices for food production.

Enhancement of Paenibacillus sp. D9 Lipopeptide Biosurfactant Production Through the Optimization of Medium Composition and Its Application for Biodegradation of Hydrophobic Pollutants.

Interests in biosurfactant in industrial and environmental applications have increased considerably in recent years, owing to their potential benefits over synthetic counterparts. The present study aimed at analyzing the stability and oil removal efficiency of a new lipopeptide biosurfactant produced by Paenibacillus sp. D9 and its feasibility of its use in biotechnological applications. Paenibacillus sp. D9 was evaluated for optimal growth conditions and improved production yield of lipopeptide biosurfactant with variations in different substrate parameters such as carbon (C), nitrogen (N), C:N: ratio, metal supplements, pH, and temperature. Enhanced biosurfactant production was observed when using diesel fuel and ammonium sulfate as carbon and nitrogen source respectively. The maximum biosurfactant yield of 4.11 g/L by Paenibacillus sp. D9 occurred at a C/N ratio of 3:1, at pH 7.0, 30 °C, 4.0 mM MgSO4, and 1.5% inoculum size. The D9 biosurfactant was found to retain surface-active properties under the extreme conditions such as high thermal, acidic, alkaline, and salt concentration. The ability to emulsify further emphasizes its potential usage in biotechnological application. Additionally, the lipopeptide biosurfactant exhibited good performance in the degradation of highly toxic substances when compared with chemical surfactant, which proposes its probable application in biodegradation, microbial-enhanced oil recovery or bioremediation. Furthermore, the biosurfactants were effective in a test to stimulate the solubilization of hydrophobic pollutants in both liquid environments removing 49.1 to 65.1% diesel fuel including hydrophobic pollutants. The study highlights the usefulness of optimization of culture parameters and their effects on biosurfactant production, high stability, improved desorption, and solubilization of hydrophobic pollutants.

Quantitative evaluation of different fractions of extracellular polymeric substances derived from Paenibacillus mucilaginosus against the toxicity of gold ions.

The reductive detoxification of microbes is of significant importance as toxic high oxidation-state metals are ubiquitous in the environment. As a protective interface, extracellular polymeric substances (EPS) are known to play an important role in reducing the toxicity, the relative contribution of different EPS fractions in the process of microbial reductive detoxification remains not to be understood. In this study, we used toxic gold ions (Au3+) and EPS fractions from Paenibacillus mucilaginosus as an example to quantitatively assess the relative contribution of different EPS fractions in the process of the reductive detoxification. At different concentrations of EPS (300 mg/L to 500 mg/L), B-EPS contributed higher reductive ratio (10.6%±0.6% to 25.9%±0.3%) for reducing the toxicity of Au3+, while it was lower (1.7%±0.3% to 5.4%±0.6%) for L-EPS. Confronted with the attack of the Au3+ ions (0 ppm-180 ppm), sugars in B-EPS had a more positive metabolic response than proteins (secreted sugars/ proteins>1) against the toxicity of Au3+. Ultimately, FTIR and electrochemical titration analyses showed that the detoxification process of microbial EPS was mainly mediated by the aldehyde groups of sugars in B-EPS. This study contributed a quantitative understanding for the role of different fractions of EPS in microbial defense against the attack of toxic metal ions.

Paenibacillus assamensis in Joint Fluid of Man with Suspected Tularemia, China.

Paenibacillus assamensis is a bacterium usually found in warm springs. We detected P. assamensis in a man with suspected tularemia. The strain isolated from the man's knee joint fluid was identified as P. assamensis after analysis of a homologous sequence of the 16S rRNA gene.

Combined Drug Resistance Mutations Substantially Enhance Enzyme Production in Paenibacillus agaridevorans.

This study shows that sequential introduction of drug resistance mutations substantially increased enzyme production in Paenibacillus agaridevorans The triple mutant YT478 (rsmG Gln225→stop codon, rpsL K56R, and rpoB R485H), generated by screening for resistance to streptomycin and rifampin, expressed a 1,100-fold-larger amount of the extracellular enzyme cycloisomaltooligosaccharide glucanotransferase (CITase) than the wild-type strain. These mutants were characterized by higher intracellular S-adenosylmethionine concentrations during exponential phase and enhanced protein synthesis activity during stationary phase. Surprisingly, the maximal expression of CITase mRNA was similar in the wild-type and triple mutant strains, but the mutant showed greater CITase mRNA expression throughout the growth curve, resulting in enzyme overproduction. A metabolome analysis showed that the triple mutant YT478 had higher levels of nucleic acids and glycolysis metabolites than the wild type, indicating that YT478 mutant cells were activated. The production of CITase by the triple mutant was further enhanced by introducing a mutation conferring resistance to the rare earth element, scandium. This combined drug resistance mutation method also effectively enhanced the production of amylases, proteases, and agarases by P. agaridevorans and Streptomyces coelicolor This method also activated the silent or weak expression of the P. agaridevorans CITase gene, as shown by comparisons of the CITase gene loci of P. agaridevorans T-3040 and another cycloisomaltooligosaccharide-producing bacterium, Paenibacillus sp. strain 598K. The simplicity and wide applicability of this method should facilitate not only industrial enzyme production but also the identification of dormant enzymes by activating the expression of silent or weakly expressed genes.IMPORTANCE Enzyme use has become more widespread in industry. This study evaluated the molecular basis and effectiveness of ribosome engineering in markedly enhancing enzyme production (>1,000-fold). This method, due to its simplicity, wide applicability, and scalability for large-scale production, should facilitate not only industrial enzyme production but also the identification of novel enzymes, because microorganisms contain many silent or weakly expressed genes which encode novel antibiotics or enzymes. Furthermore, this study provides a new mechanism for strain improvement, with a consistent rather than transient high expression of the key gene(s) involved in enzyme production.

Enhanced utilization of fluorene by Paenibacillus sp. PRNK-6: Effect of rhamnolipid biosurfactant and synthetic surfactants.

The present investigation was to study the effect of different non-ionic surfactants (Tween-80, Tween-60, Tween-40, Tween-20, Triton X-100) and a rhamnolipid biosurfactant on the degradation of fluorene by Paenibacillus sp. PRNK-6. An enhancement in the growth, as well as fluorene utilization by this strain were observed in the presence of biosurfactant and non-ionic surfactants except Tween-20 and Triton X-100. Triton X-100 and Tween-20 were toxic to this bacterium. The strain PRNK-6 utilized 75% of fluorene (280mg/L) in 24h in an unamended condition. On the other hand, the complete utilization of higher concentration fluorene (320mg/L) by this strain was noticed when the medium was amended with Tween-80 (1.5% v/v) within 24h of incubation. Whereas, 90.6%, 96.5% and 96.7% of fluorene (280mg/L) was utilized when amended with Tween-60 (3.5% v/v), Tween-40 (3% v/v) and biosurfactant (25mg/L) respectively. Biosurfactant promoted the fluorene degradation potential of PRNK-6 as 96.2% of 320mg/L fluorene was degraded within 24h. Further, the added tween series surfactants and a biosurfactant have increased the cell surface hydrophobicity of the PRNK-6. Thus correlating with the enhanced degradation of the fluorene.

The complex resistomes of Paenibacillaceae reflect diverse antibiotic chemical ecologies.

The ecology of antibiotic resistance involves the interplay of a long natural history of antibiotic production in the environment, and the modern selection of resistance in pathogens through human use of these drugs. Important components of the resistome are intrinsic resistance genes of environmental bacteria, evolved and acquired over millennia, and their mobilization, which drives dissemination in pathogens. Understanding the dynamics and evolution of resistance across bacterial taxa is essential to address the current crisis in drug-resistant infections. Here we report the exploration of antibiotic resistance in the Paenibacillaceae prompted by our discovery of an ancient intrinsic resistome in Paenibacillus sp. LC231, recovered from the isolated Lechuguilla cave environment. Using biochemical and gene expression analysis, we have mined the resistome of the second member of the Paenibacillaceae family, Brevibacillus brevis VM4, which produces several antimicrobial secondary metabolites. Using phylogenomics, we show that Paenibacillaceae resistomes are in flux, evolve mostly independent of secondary metabolite biosynthetic diversity, and are characterized by cryptic, redundant, pseudoparalogous, and orthologous genes. We find that in contrast to pathogens, mobile genetic elements are not significantly responsible for resistome remodeling. This offers divergent modes of resistome development in pathogens and environmental bacteria.

Effects of organochlorine pesticides on plant growth-promoting traits of phosphate-solubilizing rhizobacterium, Paenibacillus sp. IITISM08.

The study aimed to identify an effective phosphate-solubilizing and organochlorine pesticide-tolerant bacterial strain(s). A total of 50 phosphate-solubilizing bacterial (PSB) strains were isolated from pesticide-stressed soil. Ten isolates showing higher solubilization were selected for organochlorine pesticides (endosulfan, aldrin, and lindane) tolerance. The strain IITISM08 showed the maximum potential of phosphorous solubilization in Pikovaskya agar medium (solubilization index = 3.2) and in broth medium (348 ± 2 µg mL-1) and tolerated up to 250 µg mL-1 of organochlorine pesticides. During phosphorous solubilization, the presence of functional group and organic acid production were also observed using FT-IR and HPLC. The plant growth-promoting (PGP) traits of the strain IITISM08 was highly inhibited in presence of endosulfan among the three organochlroine pesticides. The strain IITISM08 degraded aldrin (79%), lindane (68%), and endosulfan (51%) at a concentration of 50 µg mL-1. The strain IITISM08 was identified using 16S rDNA gene sequencing as Paenibacillus sp. (IITISM08). The study revealed that the strain IITISM08 can be used as PGP candidate even under organochlorine pesticide-stressed condition.

Biocidal properties of maltose reduced silver nanoparticles against American foulbrood diseases pathogens.

Bee disease caused by spore-forming Paenibacillus larvae and Paenibacillus alvei is a serious problem for honey production. Thus, there is an ongoing effort to find an effective agent that shows broad biocidal activity with minimal environmental hazard. In this study, the biocidal effect of maltose reduced silver nanoparticles (AgNPs) is evaluated against American foulbrood and European foulbrood pathogens. The results demonstrate that the maltose reduced AgNPs are excellent short and long-term biocides against P. larvae isolates. The long-term effect suggests that the Ag+ ions are released from the AgNPs with increasing time in a controlled manner.

Structural analysis and enhanced production of fusaricidin from Paenibacillus kribbensis CU01 isolated from yellow loess.

A bacterial strain showing strong antifungal activity was isolated from yellow loess and was identified as Paenibacillus kribbensis CU01. Insoluble mucoidal polymers were separated from M9 culture medium via low-speed centrifugation. Most antifungal activity was associated with substances in the insoluble precipitate, which was purified by reverse phase high performance liquid chromatography. Purified fractions were analyzed using matrix-assisted laser desorption/ionization time-of-flight/time-of-flight mass spectrometry. Two major ion peaks with mass-to-charge ratio values (m/z) at 883.6 and 897.6 were revealed. After alkaline hydrolysis and sequence analysis, two cyclic depsipeptides were identified as, fusaricidin A and fusaricidin B. Their production was significantly increased by the addition of glucose, Fe2+ , and Mn2+ to M9 medium. Maximum concentrations of produced fusaricidin A and fusaricidin B at flask-scale comprised 460 mg L-1 and 118 mg L-1 , respectively: the highest production concentrations yet reported in the literature. This demonstrates that P. kribbensis CU01 has enormous commercial potential for the mass production of fusaricidin.

An extractive membrane biofilm reactor as alternative technology for the treatment of methyl tert-butyl ether contaminated water.

Among the strategies developed for contaminated groundwater bioremediation, those based on the use of bacteria adhering to inert supports and establishing biofilms have gained great importance in this field. Extractive membrane biofilm reactor (EMBFR) technology offers productive solutions for the removal of volatile and semi-volatile compounds. EMBFR technology is based on the use of extractive semipermeable membranes through which contaminants migrate to the biological compartment in which microorganisms with pollutant biotransformation and/or mineralization capacities can grow, forming an active biofilm on the membrane surface. The objective of this study was to assess the use of three bacterial strains (Paenibacillus sp. SH7 CECT 8558, Agrobacterium sp. MS2 CECT 8557, and Rhodococcus ruber EE6 CECT 8612), as inoculum in a lab-scale EMBFR running for 28 days under aerobic conditions to eliminate methyl tert-butyl ether (MTBE) from water samples. Three different hydraulic retention times (1, 6, and 12 h) were employed. MTBE degradation values were determined daily by a gas GC-MS technique, as well as suspended bacterial growth. The biofilm established by the bacterial strains on the semipermeable membrane was detected by Field-Emission Scanning Electron Microscopy (FESEM) at the end of each experiment. The acute toxicity of the treated effluents and biomedium was determined by Microtox© assay (EC50 ).The results achieved from the MTBE degradation, biofilm formation, and toxicity analysis indicated that bacterial strains MS2 and EE6 were the best options as selective inoculum, although further research is needed, particularly with regard to their possible use as a mixed culture. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:1238-1245, 2016.

Identification of pigmented Serratia marcescens symbiotically associated with Rhynchophorus ferrugineus Olivier (Coleoptera: Curculionidae).

To characterize red pigment-producing bacteria (RPPB) regularly released during oviposition by red palm weevil (RPW), RPPB were recovered from eggs deposited in apples supplied as substrate for oviposition. The presence of RPPB was also detected from gut, the reproductive apparatus of dissected adult and virgin insects and from pupal cases collected within infested palms. RPPB were also identified all along the tissue of these palms. Analysis of the 16S rDNA, gyrB, rpoB, recA, and groEL sequences assigned RPPB to the species Serratia marcescens. RPPB exhibited an antimicrobial activity assessed by the agar well diffusion method against a number of gram-positive and gram-negative bacteria. In this study, we first report the identification of a red pigment-producing S. marcescens as extracellular symbiont of RPW. Route of transmission, detection within different organs, and a wide spread along the infested palm tissue, suggested S. marcescens is present as extracellular symbiont in different developmental stages of the RPW. Additionally, the antimicrobial activity exhibited versus Bacillus spp., Paenibacillus spp., and Lysinibacillus spp., reported as insect pathogens and potential candidates for biocontrol agents, could ascribe for S. marcescens a potential protective role.

A novel type bacterial flagellar motor that can use divalent cations as a coupling ion.

The bacterial flagellar motor is a sophisticated nanomachine embedded in the cell envelope and powered by an electrochemical gradient of H(+), Na(+), or K(+)across the cytoplasmic membrane. Here we describe a new member of the bacterial flagellar stator channel family (MotAB1 of Paenibacillus sp. TCA20 (TCA-MotAB1)) that is coupled to divalent cations (Ca(2+)and Mg(2+)). In the absence of divalent cations of alkaline earth metals, no swimming was observed in Paenibacillus sp. TCA20, which grows optimally in Ca(2+)-rich environments. This pattern was confirmed by swimming assays of a stator-free Bacillus subtilis mutant expressing TCA-MotAB1. Both a stator-free and major Mg(2+)uptake system-deleted B. subtilis mutant expressing TCA-MotAB1 complemented both growth and motility deficiency under low Mg(2+)conditions and exhibited [Mg(2+)]in identical to that of the wild-type. This is the first report of a flagellar motor that can use Ca(2+)and Mg(2+)as coupling ions. These findings will promote the understanding of the operating principles of flagellar motors and molecular mechanisms of ion selectivity.