Co-inoculation with novel nodule-inhabiting bacteria reduces the benefits of legume-rhizobium symbiosis.

The ecologically and economically vital symbiosis between nitrogen-fixing rhizobia and leguminous plants is often thought of as a bi-partite interaction, yet studies increasingly show the prevalence of non-rhizobial endophytes (NREs) that occupy nodules alongside rhizobia. Yet, what impact these NREs have on plant or rhizobium fitness remains unclear. Here, we investigated four NRE strains found to naturally co-occupy nodules of the legume Medicago truncatula alongside Sinorhizobium meliloti in native soils. Our objectives were to (1) examine the direct and indirect effects of NREs on M. truncatula and S. meliloti fitness, and (2) determine whether NREs can re-colonize root and nodule tissues upon reinoculation. We identified one NRE strain (522) as a novel Paenibacillus species, another strain (717A) as a novel Bacillus species, and the other two (702A and 733B) as novel Pseudomonas species. Additionally, we found that two NREs (Bacillus 717A and Pseudomonas 733B) reduced the fitness benefits obtained from symbiosis for both partners, while the other two (522, 702A) had little effect. Lastly, we found that NREs were able to co-infect host tissues alongside S. meliloti. This study demonstrates that variation of NREs present in natural populations must be considered to better understand legume-rhizobium dynamics in soil communities.

Paenibacillus terrae NK3-4 regulates the transcription of growth-related and stress resistance-related genes in rice.

Paenibacillus terrae NK3-4 is a plant growth-promoting rhizobacterium. In this study, the effects of NK3-4 on rice growth and gene transcription were determined. The results indicated that a seed soaking treatment and a pre-germination seed treatment using NK3-4 promoted rice growth, especially spraying rice seedlings with NK3-4 increased the root number and root length by 34.2% and 34.1%, respectively. Moreover, NK3-4 induced the differential transcription of genes annotated with gene ontology (GO) terms; the number of up-regulated genes was 4.38-times higher than the number of down-regulated genes. The NK3-4 treatment induced the differential transcription of genes in 1794 GO functional groups, with 1531 functional groups containing up-regulated genes. Specific growth-related genes up-regulated by NK3-4 are involved in biological processes, including responses to auxin, hormone biosynthesis, cellular component biogenesis, root system development, and other functions. Furthermore, stress resistance-related genes were up-regulated, some of which encode WRKYs, NPK1-related protein kinase, NPR1-like 4, CaM-like proteins, MYBs, ERFs, TIFYs, NACs, EL5s, PR1s, PR2, PR8, PODs, and PAD4. Considered together, these findings imply that NK3-4 may promote plant growth and enhance stress resistance by regulating gene expression, making it a potentially useful microbe for regulating rice growth and stress resistance.

Metabolic Profiling of Interspecies Interactions During Sessile Bacterial Cultivation Reveals Growth and Sporulation Induction in Paenibacillus amylolyticus in Response to Xanthomonas retroflexus.

The toolbox available for microbiologists to study interspecies interactions is rapidly growing, and with continuously more advanced instruments, we are able to expand our knowledge on establishment and function of microbial communities. However, unravelling molecular interspecies interactions in complex biological systems remains a challenge, and interactions are therefore often studied in simplified communities. Here we perform an in-depth characterization of an observed interspecies interaction between two co-isolated bacteria, Xanthomonas retroflexus and Paenibacillus amylolyticus. Using microsensor measurements for mapping the chemical environment, we show how X. retroflexus promoted an alkalization of its local environment through degradation of amino acids and release of ammonia. When the two species were grown in proximity, the modified local environment induced a morphological change and growth of P. amylolyticus followed by sporulation. 2D spatial metabolomics enabled visualization and mapping of the degradation of oligopeptide structures by X. retroflexus and morphological changes of P. amylolyticus through e.g. the release of membrane-associated metabolites. Proteome analysis and microscopy were used to validate the shift from vegetative growth towards sporulation. In summary, we demonstrate how environmental profiling by combined application of microsensor, microscopy, metabolomics and proteomics approaches can reveal growth and sporulation promoting effects resulting from interspecies interactions.

Preparation of chitosan from waste shrimp shells fermented with Paenibacillus jamilae BAT1.

In this study, chitin extraction from shrimp shell powder (SSP) using locally isolated Paenibacillus jamilae BAT1 (GenBank: MN176658), the preparation of chitosan from the extracted chitin, and the characterization and biological activity (antimicrobial and antioxidant) of the prepared chitosan (PC) were investigated. It was determined that P. jamilae BAT1 did not have chitinase activity but showed high protease activity and protein removal potential. Optimum pH, shell concentration and incubation time for deproteinization were determined as 7.0, 60 g/L and 4 days, respectively. Addition of KH2PO4 or MgSO4 did not affect chitin extraction and deproteinization yield. The maximum yields of deproteinization, demineralization and chitin extraction yields were 87.67, 41.95 and 24.5%, respectively. The viscosity-average molecular weight of PC was determined as 1.41 × 105 g/mol. The deacetylation degree of PC (86%) was found to be higher that of commercial chitosan (CC) (78%). DPPH scavenging activity of PC (IC50 0.59 mg/mL) was higher than that of CC (IC50 3.72 mg/mL). PC was found to have higher antimicrobial activity against the bacteria E. coli and S. aureus and the yeast C. albicans when compared to CC. This is the first study on the use of the bacterium P. jamilae in biological chitin extraction.

Bacterial-induced pH shifts link individual cell physiology to macroscale collective behavior.

Bacteria have evolved a diverse array of signaling pathways that enable them to quickly respond to environmental changes. Understanding how these pathways reflect environmental conditions and produce an orchestrated response is an ongoing challenge. Herein, we present a role for collective modifications of environmental pH carried out by microbial colonies living on a surface. We show that by collectively adjusting the local pH value, Paenibacillus spp., specifically, regulate their swarming motility. Moreover, we show that such pH-dependent regulation can converge with the carbon repression pathway to down-regulate flagellin expression and inhibit swarming in the presence of glucose. Interestingly, our results demonstrate that the observed glucose-dependent swarming repression is not mediated by the glucose molecule per se, as commonly thought to occur in carbon repression pathways, but rather is governed by a decrease in pH due to glucose metabolism. In fact, modification of the environmental pH by neighboring bacterial species could override this glucose-dependent repression and induce swarming of Paenibacillus spp. away from a glucose-rich area. Our results suggest that bacteria can use local pH modulations to reflect nutrient availability and link individual bacterial physiology to macroscale collective behavior.

Diazotroph Paenibacillus triticisoli BJ-18 Drives the Variation in Bacterial, Diazotrophic and Fungal Communities in the Rhizosphere and Root/Shoot Endosphere of Maize.

Application of diazotrophs (N2-fixing microorganisms) can decrease the overuse of nitrogen (N) fertilizer. Until now, there are few studies on the effects of diazotroph application on microbial communities of major crops. In this study, the diazotrophic and endospore-forming Paenibacillus triticisoli BJ-18 was inoculated into maize soils containing different N levels. The effects of inoculation on the composition and abundance of the bacterial, diazotrophic and fungal communities in the rhizosphere and root/shoot endosphere of maize were evaluated by sequencing the 16S rRNA, nifH gene and ITS (Inter Transcribed Spacer) region. P. triticisoli BJ-18 survived and propagated in all the compartments of the maize rhizosphere, root and shoot. The abundances and diversities of the bacterial and diazotrophic communities in the rhizosphere were significantly higher than in both root and shoot endospheres. Each compartment of the rhizosphere, root and shoot had its specific bacterial and diazotrophic communities. Our results showed that inoculation reshaped the structures of the bacterial, diazotrophic and fungal communities in the maize rhizosphere and endosphere. Inoculation reduced the interactions of the bacteria and diazotrophs in the rhizosphere and endosphere, while it increased the fungal interactions. After inoculation, the abundances of Pseudomonas, Bacillus and Paenibacillus in all three compartments, Klebsiella in the rhizosphere and Paenibacillus in the root and shoot were significantly increased, while the abundances of Fusarium and Giberella were greatly reduced. Paenibacillus was significantly correlated with plant dry weight, nitrogenase, N2-fixing rate, P solubilization and other properties of the soil and plant.

Influence of soil microbes on Escherichia coli O157:H7 survival in soil rinse and artificial soil.

AIMS: This research investigated the influence of soil microbiota on Escherichia coli O157:H7 survival in soil rinse and artificial soil. Additionally, the influence of selected soil bacteria on E. coli O157:H7 in soil environments was determined. METHODS AND RESULTS: Escherichia coli O157:H7 counts (log CFU per ml or g-1 ) were determined by spread plating: (i) artificial soil amended with soil rinse (filter-sterilized and unfiltered) at 30°C; (ii) unfiltered soil rinse (50 ml) treated with cycloheximide (200 µg ml-1 ), vancomycin (40 µg ml-1 ), heat (80°C, 15 min) and no treatment (control) for 7 days at 30°C and (iii) filtered soil rinse with selected soil bacterial isolates over 7 days. There was a significant difference (P = 0·027) in E. coli O157:H7 counts after 35 days between artificial soils amended with filtered (4·45 ± 0·29) and non-filtered (1·83 ± 0·33) soil rinse. There were significant differences (P < 0·05) in E. coli O157:H7 counts after 3 days of incubation between soil rinse treatments (heat (7·04 ± 0·03), cycloheximide (6·94 ± 0·05), vancomycin (4·26 ± 0·98) and control (5·00 ± 0·93)). Lastly, a significant difference (P < 0·05) in E. coli O157:H7 counts was observed after 3 days of incubation at 30°C in filtered soil rinse when incubated with Paenibacillus alvei versus other soil bacterial isolates evaluated. CONCLUSIONS: Soil microbiota isolated from Florida sandy soil influenced E. coli O157:H7 survival. Specifically, P. alvei reduced E. coli O157:H7 by over 3 log CFU per ml after 3 days of incubation at 30°C in filtered soil rinse. SIGNIFICANCE AND IMPACT OF THE STUDY: This research identified soil bacterial isolates that may reduce E. coli O157:H7 in the soil environment and be used in future biocontrol applications.

Paenibacillus puerhi sp. nov., isolated from the rhizosphere soil of Pu-erh tea plants (Camellia sinensis var. assamica).

An aerobic, Gram-staining-positive, rod-shaped, endospore-forming and motile bacterial strain, designated SJY2T, was isolated from the rhizosphere soil of tea plants (Camellia sinensis var. assamica) collected in the organic tea garden of the Jingmai Pu-erh tea district in Pu'er city, Yunnan, southwest China. Phylogenetic analysis based on 16S rRNA gene sequences showed that the isolate belonged to the genus Paenibacillus. The closest phylogenetic relative was Paenibacillus filicis DSM 23916T (98.1% similarity). The major fatty acids (> 10% of the total fatty acids) were anteiso-C15:0 and isoC16:0. The major respiratory quinone was MK-7 and the major polar lipid was diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine and phosphatidylmonomethylethanolamine. The peptidoglycan contained glutamic acid, serine, alanine and meso-diaminopimelic acid. Genome sequencing revealed a genome size of 6.71 Mbp and a G + C content of 53.1%. Pairwise determined whole genome average nucleotide identity (gANI) values and digital DNA-DNA hybridization (dDDH) values suggested that strain SJY2T represents a new species, for which we propose the name Paenibacillus puerhi sp. nov. with the type strain SJY2T (= CGMCC 1.17156T = KCTC 43242T).

Coupling Ion Specificity of the Flagellar Stator Proteins MotA1/MotB1 of Paenibacillus sp. TCA20.

The bacterial flagellar motor is a reversible rotary molecular nanomachine, which couples ion flux across the cytoplasmic membrane to torque generation. It comprises a rotor and multiple stator complexes, and each stator complex functions as an ion channel and determines the ion specificity of the motor. Although coupling ions for the motor rotation were presumed to be only monovalent cations, such as H+ and Na+, the stator complex MotA1/MotB1 of Paenibacillus sp. TCA20 (MotA1TCA/MotB1TCA) was reported to use divalent cations as coupling ions, such as Ca2+ and Mg2+. In this study, we initially aimed to measure the motor torque generated by MotA1TCA/MotB1TCA under the control of divalent cation motive force; however, we identified that the coupling ion of MotA1TCAMotB1TCA is very likely to be a monovalent ion. We engineered a series of functional chimeric stator proteins between MotB1TCA and Escherichia coli MotB. E. coli ΔmotAB cells expressing MotA1TCA and the chimeric MotB presented significant motility in the absence of divalent cations. Moreover, we confirmed that MotA1TCA/MotB1TCA in Bacillus subtilis ΔmotABΔmotPS cells generates torque without divalent cations. Based on two independent experimental results, we conclude that the MotA1TCA/MotB1TCA complex directly converts the energy released from monovalent cation flux to motor rotation.

Heavy metals-resistant bacteria (HM-RB): Potential bioremediators of heavy metals-stressed Spinacia oleracea plant.

Microorganism technologies can provide a potential alternative to traditional methods of removing heavy metals to conserve agricultural soils. This study aimed to identify and characterize heavy metals-resistant bacteria (HM-RB) isolated from industry-affected soil and their desired impact as bioremediators of heavy metals-stressed spinach plants. Three of 135 isolates were selected based on a high level of resistance to heavy metals. Based on morphological and biochemical characteristics, the selected isolates were identified as Bacillus subtilis subsp. spizizenii DSM 15029 T DSM (MA3), Paenibacillus jamilae DSM 13815 T DSM (LA22), or Pseudomonas aeruginosa DSM 1117 DSM (SN36). Experiments were implemented to investigate the three isolated HM-RB ability on improving attributes of growth, physio-biochemistry, and components of the antioxidant defense system of spinach plant exposed to the stress of cadmium (Cd2+; 2 mM), lead (Pb2+; 2 mM) or 2 mM Cd2++2 mM Pb2+. Compared to control, Cd2+ or Pb2+ stress markedly lowered plant fresh and dry weights, leaf contents of chlorophylls and carotenoids, rates of transpiration (Tr), net photosynthesis (Pn) and stomatal conductance (gs), relative water content (RWC), and membrane stability index (MSI). In contrast, contents of α.tochopherol (α.TOC), ascorbic acid (AsA), glutathione (GSH), proline, soluble sugars, Cd2+, and Pb2+, as well as activities of enzymatic and non-enzymatic antioxidants were markedly elevated. The application of HM-RB promoted the tolerance to heavy metal stress in spinach plants by improving Tr, Pn, gs, RWC, and MSI, while activities of enzymatic and non-enzymatic antioxidants were suppressed. These results reflected positively in promoting plant growth under heavy metal stress. Therefore, the application of HM-RB as potential bioremediators may be a promising strategy for promoting plant growth and productivity under heavy metal stress.

Complete Genome Sequence of Paenibacillus sp. JZ16, a Plant Growth Promoting Root Endophytic Bacterium of the Desert Halophyte Zygophyllum Simplex.

Paenibacillus sp. JZ16 is a gram-positive, rod-shaped, motile root endophytic bacterium of the pioneer desert halophytic plant Zygophyllum simplex. JZ16 was previously shown to promote salinity stress tolerance in Arabidopsis thaliana and possesses a highly motile phenotype on nutrient agar. JZ16 genome sequencing using PacBio generated 82,236 reads with a mean insert read length of 11,432 bp and an estimated genome coverage of 127X, resulting in a chromosome of 7,421,843 bp with a GC content of 49.25% encoding 6710 proteins, 8 rRNA operons, 117 ncRNAs and 73 tRNAs. Whole-genome sequencing analysis revealed a potentially new species for JZ16. Functional analysis revealed the presence of a number of enzymes involved in the breakdown of plant-based polymers. JZ16 could be of potential use in agricultural applications for promoting biotic and abiotic stress tolerance and for biotechnological processes (e.g., as biocatalysts for biofuel production). The culture-dependent collection of bacterial endophytes from desert plants combined with genome sequence mining provides new opportunities for industrial applications.

Inoculation of Lupinus albus with the nodule-endophyte Paenibacillus glycanilyticus LJ121 improves grain nutritional quality.

Metabolic changes occurring in white lupine grain were investigated in response to Plant Growth Promoting Rhizobacteria (PGPR) root inoculation under field condition. We precisely targeted lipids and phenolics changes occurring in white lupine grain in response to Pseudomonas brenneri LJ215 and/or Paenibacillus glycanilyticus LJ121 inoculation. Lipids and phenolic composition were analyzed using an Ultra High-Performance Liquid Chromatography/Tandem Mass Spectrometry Methods. As compared to grain of un-inoculated control plant, Paenibacillus glycaniliticus inoculation highly increased the total lipids content (from 232.55 in seeds of un-inoculated control plant to 944.95 mg/kg) and the relative percentage of several fatty acid such as oleic acid (+20.95%) and linoleic acid (+14.28%) and decreased the relative percentage of glycerophospholipids (- 13.11%), sterol (- 0.2% and - 0.34% for stigmasterol and campesterol, respectively) and prenol (- 17.45%) class. Paenibacillus glycaniliticus inoculation did not affect total phenolic content, while it modulated content of individual phenolic compounds and induced the accumulation of "new" phenolics compounds such as kaempferol. Paenibacillus glycanilyticus LJ121 can be a useful bio-fertilizer to enhance nutritional quality of white lupine grain.

Isolation, identification and plant growth promotion ability of endophytic bacteria associated with lupine root nodule grown in Tunisian soil.

The present study aims to characterize nodule endophytic bacteria of spontaneous lupine plants regarding their diversity and their plant growth promoting (PGP) traits. The potential of PGPR inoculation was investigated to improve white lupine growth across controlled, semi-natural and field conditions. Lupinus luteus and Lupinus angustifolius nodules were shown inhabited by a large diversity of endophytes. Several endophytes harbor numerous plant growth promotion traits such as phosphates solubilization, siderophores production and 1-aminocyclopropane-1-carboxylate deaminase activity. In vivo analysis confirmed the plant growth promotion ability of two strains (Paenibacillus glycanilyticus LJ121 and Pseudomonas brenneri LJ215) in both sterilized and semi-natural conditions. Under field conditions, the co-inoculation of lupine by these strains increased shoot N content and grain yield by 25% and 36%, respectively. These two strains Paenibacillus glycanilyticus LJ121 and Pseudomonas brenneri LJ215 are effective plant growth-promoting bacteria and they may be used to develop an eco-friendly biofertilizer to boost white lupine productivity.

Plantibacter flavus, Curtobacterium herbarum, Paenibacillus taichungensis, and Rhizobium selenitireducens Endophytes Provide Host-Specific Growth Promotion of Arabidopsis thaliana, Basil, Lettuce, and Bok Choy Plants.

A collection of bacterial endophytes isolated from stem tissues of plants growing in soils highly contaminated with petroleum hydrocarbons were screened for plant growth-promoting capabilities. Twenty-seven endophytic isolates significantly improved the growth of Arabidopsis thaliana plants in comparison to that of uninoculated control plants. The five most beneficial isolates, one strain each of Curtobacterium herbarum, Paenibacillus taichungensis, and Rhizobium selenitireducens and two strains of Plantibacter flavus were further examined for growth promotion in Arabidopsis, lettuce, basil, and bok choy plants. Host-specific plant growth promotion was observed when plants were inoculated with the five bacterial strains. P. flavus strain M251 increased the total biomass and total root length of Arabidopsis plants by 4.7 and 5.8 times, respectively, over that of control plants and improved lettuce and basil root growth, while P. flavus strain M259 promoted Arabidopsis shoot and root growth, lettuce and basil root growth, and bok choy shoot growth. A genome comparison between P. flavus strains M251 and M259 showed that both genomes contain up to 70 actinobacterial putative plant-associated genes and genes involved in known plant-beneficial pathways, such as those for auxin and cytokinin biosynthesis and 1-aminocyclopropane-1-carboxylate deaminase production. This study provides evidence of direct plant growth promotion by Plantibacter flavusIMPORTANCE The discovery of new plant growth-promoting bacteria is necessary for the continued development of biofertilizers, which are environmentally friendly and cost-efficient alternatives to conventional chemical fertilizers. Biofertilizer effects on plant growth can be inconsistent due to the complexity of plant-microbe interactions, as the same bacteria can be beneficial to the growth of some plant species and neutral or detrimental to others. We examined a set of bacterial endophytes isolated from plants growing in a unique petroleum-contaminated environment to discover plant growth-promoting bacteria. We show that strains of Plantibacter flavus exhibit strain-specific plant growth-promoting effects on four different plant species.

A multifaceted rhizobacterium Paenibacillus lentimorbus alleviates nutrient deficiency-induced stress in Cicer arietinum L.

Nutrient deficiency in soil is one of the limiting factors responsible for stunted growth and poor flowering/fruiting of crops which result in decline in overall agricultural productivity. However, one important strategy to overcome the problem of nutrient deficiency and to avoid use of chemical fertilizers is the use of plant growth promoting rhizobacteria (PGPR). Paenibacillus lentimorbus NRRL B-30488 (hereafter B-30488), an efficient PGPR has been reported to have various plant growth promoting traits that help crops to mitigate various environmental stresses. Therefore, the present work was designed to examine the application of B-30488 on chickpea growth under nutrient stress condition. Plants inoculated with B-30488 showed positive modulation in physio-biochemical behaviour and mineral nutrient uptake for better growth and development. Alteration in gene expression and metabolic profile under nutrient stress condition in chickpea also supported the stress amelioration capability of B-30488. Principal component analysis statistically proved that improved growth performance of chickpea plants under nutrient stress was mainly due to B-30488 induced modulation of metabolic pathways. To the best of our knowledge, this is the first study for analysis of growth promotion and stress alleviation in chickpea plants subjected to nutrient stress in presence of PGPR B-30488.

Culturable endophytic bacteria of Camellia species endowed with plant growth promoting characteristics.

AIM: Tea (Camellia sinensis (L.) O. Kuntze) is an economically important caffeine-containing beverage crop with massive plantation in the Northeast corner of the agroclimatic belt of India. The main aim of the work was to isolate, identify and characterize the native plant growth promoting endophytes associated with tea for future microbe based bioformulation. METHODS AND RESULTS: A total of 129 endophytic bacteria were isolated and characterized for plant growth promoting traits such as indole-3-acetic acid (IAA), phosphate solubilization, ammonia production, biocontrol traits like siderophore and extracellular enzyme production. BOX-PCR fingerprinting was used to differentiate the various bacterial isolates obtained from six different tea species. 16S rRNA sequencing and blast analysis showed that these isolates belonged to different genera, that is, Bacillus, Brevibacterium, Paenibacillus and Lysinibacillus. Lysinibacillus sp. S24 showed the highest phosphate solubilization and IAA acid production efficiency of 268·4 ± 14·3 and 13·5 ± 0·5 µg ml-1 , respectively. Brevibacterium sp. S91 showed the highest ammonia production of 6·2 ± 0·5 µmol ml-1 . Chitinase, cellulase, protease and pectinase activities were shown by 4·6, 34·1, 27·13 and 13·14% of the total isolates, respectively. Similarly, 41% of the total isolates were positive for 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase activity. Further, the potent PGP isolates, S24 and S91 were able to enhance the vegetative parameters such as dry/fresh weight of root and shoot of tea plants in nursery conditions. CONCLUSION: Our findings corroborate that tea endophytic bacteria possess the potential to demonstrate multiple PGP traits both, in vivo and in vitro and have the potential for further large-scale trials. SIGNIFICANCE AND IMPACT OF THE STUDY: The exploration of tea endophytic bacterial community is suitable for the development of bioformulations for an integrated nutrient management and thus sustainable crop production and decreasing the hazardous effects of chemical fertilizers on the environment and human health.

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.

Neither thermosonication nor cold sonication is better than pasteurization for milk shelf life.

High-power, low-frequency ultrasound has been suggested as a novel processing technique with the potential to extend milk shelf life via inactivation of bacteria and spores that survive standard pasteurization. The primary objective of this research was to determine whether short-duration (≤60 s) sonication treatment, in conjunction with pasteurization, can increase shelf life while producing no adverse aroma effect. Skim milk was inoculated with Paenibacillus amylolyticus, a spore-forming, thermotolerant and psychrophilic milk contamination bacterium. Milk was sonicated under 6 selected amplitude and time conditions, except for control. Both cold sonicated (C-S) and thermosonicated (T-S) milk and milk treatments were pasteurized; however, T-S milk was sonicated after pasteurization (72.5 ± 0.3°C; mean ± SD), whereas C-S milk was sonicated at 12.5 ± 5°C (mean ± SD) before pasteurization. Milk was refrigerated up to 50 d and total aerobic counts were enumerated on pasteurized control, C-S, and T-S milk weekly. Neither C-S nor T-S treatments reduced total aerobic counts to an equivalent level as pasteurization alone. Counts in pasteurized controls and C-S milk did not exceed 3.00 log cfu/mL for up to 50 d; counts in T-S milk exceeded 5.00 cfu/mL by d 36. Aroma qualities (cooked, lacks freshness, and rubbery) of 2 T-S treatment intensities [170 µm peak-to-peak (p-p) for 60s and 200 µmp-p for 10 s] and pasteurized controls were evaluated by a trained descriptive sensory panel. No significant differences were observed in cooked or lacks freshness aromas among samples. Only the milk treated with 170 µmp-p for 60 s had significantly higher rubbery aroma on d 1 compared with milk treated with 200 µmp-p for 10 s. Although the sensory effects of T-S on milk may not limit the commercial feasibility of cold sonication or thermosonication, conditions that differ from those used in the present study should be considered in the future. Neither C-S nor T-S were appropriate techniques for reducing bacterial count in fluid milk beyond standard pasteurization and, in fact, increased counts of spore-forming spoilage bacteria.

Wild bees and their nests host Paenibacillus bacteria with functional potential of avail.

BACKGROUND: In previous studies, the gram-positive firmicute genus Paenibacillus was found with significant abundances in nests of wild solitary bees. Paenibacillus larvae is well-known for beekeepers as a severe pathogen causing the fatal honey bee disease American foulbrood, and other members of the genus are either secondary invaders of European foulbrood or considered a threat to honey bees. We thus investigated whether Paenibacillus is a common bacterium associated with various wild bees and hence poses a latent threat to honey bees visiting the same flowers. RESULTS: We collected 202 samples from 82 individuals or nests of 13 bee species at the same location and screened each for Paenibacillus using high-throughput sequencing-based 16S metabarcoding. We then isolated the identified strain Paenibacillus MBD-MB06 from a solitary bee nest and sequenced its genome. We did find conserved toxin genes and such encoding for chitin-binding proteins, yet none specifically related to foulbrood virulence or chitinases. Phylogenomic analysis revealed a closer relationship to strains of root-associated Paenibacillus rather than strains causing foulbrood or other accompanying diseases. We found anti-microbial evidence within the genome, confirmed by experimental bioassays with strong growth inhibition of selected fungi as well as gram-positive and gram-negative bacteria. CONCLUSIONS: The isolated wild bee associate Paenibacillus MBD-MB06 is a common, but irregularly occurring part of wild bee microbiomes, present on adult body surfaces and guts and within nests especially in megachilids. It was phylogenetically and functionally distinct from harmful members causing honey bee colony diseases, although it shared few conserved proteins putatively toxic to insects that might indicate ancestral predisposition for the evolution of insect pathogens within the group. By contrast, our strain showed anti-microbial capabilities and the genome further indicates abilities for chitin-binding and biofilm-forming, suggesting it is likely a useful associate to avoid fungal penetration of the bee cuticula and a beneficial inhabitant of nests to repress fungal threats in humid and nutrient-rich environments of wild bee nests.

Paenibacillus seodonensis sp. nov., isolated from a plant of the genus Campanula.

Strain DCT-19T, representing a Gram-stain-positive, rodshaped, aerobic bacterium, was isolated from a native plant belonging to the genus Campanula on Dokdo, the Republic of Korea. Comparative analysis of the 16S rRNA gene sequence showed that this strain was closely related to Paenibacillus amylolyticus NRRL NRS-290T (98.6%, 16S rRNA gene sequence similarity), Paenibacillus tundrae A10bT (98.1%), and Paenibacillus xylanexedens NRRL B-51090T (97.6%). DNADNA hybridization indicated that this strain had relatively low levels of DNA-DNA relatedness with P. amylolyticus NRRL NRS-290T (30.0%), P. xylanexedens NRRL B-51090T (29.0%), and P. tundrae A10bT (24.5%). Additionally, the genomic DNA G + C content of DCT-19T was 44.8%. The isolated strain grew at pH 6.0-8.0 (optimum, pH 7.0), 0-4% (w/v) NaCl (optimum, 0%), and a temperature of 15-45°C (optimum 25-30°C). The sole respiratory quinone in the strain was menaquinone-7, and the predominant fatty acids were C15:0 anteiso, C16:0 iso, and C16:0. In addition, the major polar lipids were diphosphatidylglycerol and phosphatidylethanolamine. Based on its phenotypic properties, genotypic distinctiveness, and chemotaxonomic features, strain DCT-19T is proposed as a novel species in the genus Paenibacillus, for which the name Paenibacillus seodonensis sp. nov. is proposed (=KCTC 43009T =LMG 30888T). The type strain of Paenibacillus seodonensis is DCT-19T.