Habitat distribution of the genus Belliella in continental waters and the description of Belliella alkalica sp. nov., Belliella calami sp. nov. and Belliella filtrata sp. nov

The genus Belliella belongs to the family Cyclobacteriaceae (order Cytophagales, phylum Bacteroidota) and harbours aerobic chemoheterotrophic bacteria. Members of this genus were isolated from various aquatic habitats, and our analysis based on global amplicon sequencing data revealed that their relative abundance can reach up to 5-10 % of the bacterioplankton in soda lakes and pans. Although a remarkable fraction of the most frequent genotypes that we identified from continental aquatic habitats is still uncultured, five new alkaliphilic Belliella strains were characterized in detail in this study, which were isolated from three different soda lakes and pans of the Carpathian Basin (Hungary). Cells of all strains were Gram-stain-negative, obligate aerobic, rod-shaped, non-motile and non-spore-forming. The isolates were oxidase- and catalase-positive, red-coloured, but did not contain flexirubin-type pigments; they formed bright red colonies that were circular, smooth and convex. Their major isoprenoid quinone was MK-7 and the predominant fatty acids were iso-C_15 : 0, iso-C_17 : 0 3-OH and summed feature 3 containing C_16 : 1  ω6c and/or C_16 : 1  ω7c. The polar lipid profiles contained phosphatidylethanolamine, an unidentified aminophospholipid, an unidentified glycolipid, and several unidentified lipids and aminolipids. Based on whole-genome sequences, the DNA G+C content was 37.0, 37.1 and 37.8 mol % for strains R4-6^T, DMA-N-10a^T and U6F3^T, respectively. The distinction of three new species was confirmed by in silico genomic comparison. Orthologous average nucleotide identity (<85.4 %) and digital DNA-DNA hybridization values (<38.9 %) supported phenotypic, chemotaxonomic and 16S rRNA gene sequence data and, therefore, the following three novel species are proposed: Belliella alkalica sp. nov. (represented by strains R4-6^T=DSM 111903^T=JCM 34281^T=UCCCB122^T and S4-10), Belliella calami sp. nov. (DMA-N-10a^T=DSM 107340^T=JCM 34280^T=UCCCB121^T) and Belliella filtrata sp. nov. (U6F3^T=DSM 111904^T=JCM 34282^T=UCCCB123^T and U6F1). Emended descriptions of species Belliella aquatica, Belliella baltica, Belliella buryatensis, Belliella kenyensis and Belliella pelovolcani are also presented.

Biological Control of Phytopathogens: Mechanisms and Applications

According to the inherent ecological mechanisms within community structures, organismic interactions are mediated by chemical structures and signaling molecules as well as enzymatic activities targeting the vital activities of microbial competitors [...].

The Role of Bacterial Polyhydroalkanoate (PHA) in a Sustainable Future: A Review on the Biological Diversity

Environmental challenges related to the mismanagement of plastic waste became even more evident during the COVID-19 pandemic. The need for new solutions regarding the use of plastics came to the forefront again. Polyhydroxyalkanoates (PHA) have demonstrated their ability to replace conventional plastics, especially in packaging. Its biodegradability and biocompatibility makes this material a sustainable solution. The cost of PHA production and some weak physical properties compared to synthetic polymers remain as the main barriers to its implementation in the industry. The scientific community has been trying to solve these disadvantages associated with PHA. This review seeks to frame the role of PHA and bioplastics as substitutes for conventional plastics for a more sustainable future. It is focused on the bacterial production of PHA, highlighting the current limitations of the production process and, consequently, its implementation in the industry, as well as reviewing the alternatives to turn the production of bioplastics into a sustainable and circular economy.

Characterization of the Skin Cultivable Microbiota Composition of the Frog Pelophylax perezi Inhabiting Different Environments

Microorganisms that live in association with amphibian skin can play important roles in protecting their host. Within the scenarios of global change, it is important to understand how environmental disturbances, namely, metal pollution, can affect this microbiota. The aim of this study is to recognize core bacteria in the skin cultivable microbiota of the Perez frog (Pelophylax perezi) that are preserved regardless of the environmental conditions in which the frogs live. The characterization of these isolates revealed characteristics that can support their contributions to the ability of frogs to use metal impacted environments. Frog’s skin swabs were collected from P. perezi populations that inhabit a metal-polluted site and three reference (non-metal polluted) sites. Bacterial strains were isolated, identified, and subjected to an acid mine drainage tolerance (AMD) test, collected upstream from a site heavily contaminated with metals, and tested to produce extracellular polymeric substances (exopolysaccharide, EPS). All frog populations had Acinetobacter in their cutaneous cultivable microbiota. Significant growth inhibition was observed in all bacterial isolates exposed to 75% of AMD. EPS production was considered a characteristic of several isolates. The data obtained is a preliminary step but crucial to sustain that the cultivable microbiota is a mechanism for protecting frogs against environmental contamination.

Bacterial Metabolites Produced Under Iron Limitation Kill Pinewood Nematode and Attract Caenorhabditis elegans

Pine Wilt Disease (PWD) is caused by Bursaphelenchus xylophilus, the pinewood nematode, and affects several species of pine trees worldwide. The ecosystem of the Pinus pinaster trees was investigated as a source of bacteria producing metabolites affecting this ecosystem: P. pinaster trees as target-plant, nematode as disease effector and its insect-vector as shuttle. For example, metals and metal-carrying compounds contribute to the complex tree-ecosystems. This work aimed to detect novel secondary metabolites like metallophores and related molecules produced under iron limitation by PWD-associated bacteria and to test their activity on nematodes. After screening 357 bacterial strains from Portugal and United States, two promising metallophore-producing strains Erwinia sp. A41C3 and Rouxiella sp. Arv20#4.1 were chosen and investigated in more detail. The genomes of these strains were sequenced, analyzed, and used to detect genetic potential for secondary metabolite production. A combinatorial approach of liquid chromatography-coupled tandem mass spectrometry (LC-MS) linked to molecular networking was used to describe these compounds. Two major metabolites were detected by HPLC analyses and described. One HPLC fraction of strain Arv20#4.1 showed to be a hydroxamate-type siderophore with higher affinity for chelation of Cu. The HPLC fraction of strain A41C3 with highest metal affinity showed to be a catecholate-type siderophore with higher affinity for chelation of Fe. LC-MS allowed the identification of several desferrioxamines from strain Arv20#4.1, in special desferrioxamine E, but no hit was obtained in case of strain A41C3 which might indicate that it is something new. Bacteria and their culture supernatants showed ability to attract C. elegans. HPLC fractions of those supernatant-extracts of Erwinia strain A41C3, enriched with secondary metabolites such as siderophores, were able to kill pinewood nematode. These results suggest that metabolites secreted under iron limitation have potential to biocontrol B. xylophilus and for management of Pine Wilt Disease.

The endosphere of the salt marsh plant Halimione portulacoides is a diversity hotspot for the genus Salinicola: description of five novel species Salinicola halimionae sp. nov., Salinicola aestuarinus sp. nov., Salinicola endophyticus sp. nov., Salinicola halophyticus sp. nov. and Salinicola lusitanus sp. nov

Seven endophytic strains were isolated from the halophyte Halimione portulacoides, collected from Ria de Aveiro, Portugal. To determine their exact taxonomic position, comparative analyses were performed with these strains and closely related type strains of Salinicola species. Genome sequencing and comparison indicated that five of the seven isolated strains comprised distinct and novel species (average nucleotide identity <0.95; in silico DNA-DNA hybridization <70 %; G+C difference >1 %). Multilocus sequence analysis was performed using gyrB, rpoD and 16S rRNA gene sequences from the novel and type strains to determine their phylogenetic positions. The novel strains are facultative anaerobes, mesophilic, facultative alkaliphic and halophilic, test positive for catalase and oxidase activities, for hydrolysis of Tween 20 and phosphate, for production of indole-3-acetic acid, but do not produce H2S. Ubiquinone UQ-9 is present in major amounts in all strains. The major fatty acids include C16 : 0 and the summed feature containing C18 : 1ω7c and/or C18 : 1ω6c. The DNA G+C content ranges from 60.6 to 65.8 mol%. Five strains were confirmed as new species belonging to the genus Salinicola, for which the names Salinicolahalimionae sp. nov. (type strain CPA60^T=CECT 9338^T=LMG 30107^T), Salinicolaaestuarinus sp. nov. (type strain CPA62^T=CECT 9339^T=LMG 30108^T), Salinicolaendophyticus sp. nov. (type strain CPA92^T=CECT 9340^T=LMG 30109^T), Salinicolahalophyticus sp. nov. (type strain CR45^T=CECT 9341^T=LMG 30105^T) and Salinicola lusitanus sp. nov. (type strain CR50^T=CECT 9342^T=LMG 30106^T) are proposed.

The Microbiome of Endophytic, Wood Colonizing Bacteria from Pine Trees as Affected by Pine Wilt Disease

Pine wilt disease (PWD) is a devastating forest disease present worldwide. In this study we analyzed the effects of the invasion of the pinewood nematode Bursaphelenchus xylophilus, the major pathogen causing PWD, on the endophytic microbiome of adult P. pinaster trees. Wood samples from trees with different degrees of PWD disease were collected at two sites (A and M) in Portugal. Endophytic bacteria were characterized based on directly extracted DNA by fingerprinting and barcoding using the 16S rRNA gene as marker. Furthermore, cultivation-based approaches were used to obtain isolates of the major taxa to study their ecophysiology. The endophytic microbiome from P. pinaster trees differed significantly between the two sampling sites. Main bacterial OTUs belonged to the Proteobacteria (39% (site M) - 97% (site A)), and Firmicutes (0.70% (site A) - 44% (site M)). However, consequences of the invasion with the pathogen were comparable. Interestingly diversity of wood endophytic bacteria increased with the severity of the diseases, with highest diversity levels observed in in the most affected trees. Our results suggest that in the first stages of the disease, the defence mechanisms of plants are repressed by the pathogen, resulting in a colonization of the wood interior by soil microorganisms.

Diversity of cutaneous microbiome of Pelophylax perezi populations inhabiting different environments

Potential synergetic interaction between chemicals, climate change and the emergence of opportunistic diseases is of utmost concern within the amphibian decline scenario. Understand the structure and dynamic of this microbiome and how environmental stressors act on this community is a priority. The present study aimed to: i) characterize the skin microbiome of Pelophylax perezi frog by looking for variations between populations in reference and under stress conditions (one metal contaminated and another with salinity fluctuations) and ii) evaluate the tolerance of skin-isolated bacteria to chemical contamination. Skin swabs were collected from frog populations inhabiting three reference sites (LB, VA and AM), one metal-rich contaminated (TP) and one brackish lentic aquatic system (SL). The frogs' skin microbiome was characterized by culture independent method (DGGE) and by cultivation methods. DGGE showed a characteristic profile in frogs from TP population. Results of recovered communities revealed low morphotype diversity and density (Colony Forming Units per frog) on individuals from TP population, comparatively to the other sampled populations. Isolated bacteria identified based on 16S rRNA gene sequence belong mainly to the classes Actinobacteria and Alphaproteobacteria. Ecotoxicological assays with acid-metal contaminated effluent (ETP) showed that the percentage of tolerant strains was higher in frogs from TP population than in SL and LB populations. In conclusion, results suggest that: a) environmental specific characteristics, as the presence of chemical contaminants, influence the composition of amphibian microbiome, comparing with sites without such contaminants; b) there are differences in microbiome composition between populations; and c) bacteria historically exposed to effluent may evolve tolerance to this kind of contamination.

Mucilaginibacter pineti sp. nov., isolated from Pinus pinaster wood from a mixed grove of pines trees

Bacterial strain M47C3BT was isolated from the endophytic microbial community of a Pinus pinaster tree branch from a mixed grove of pines. Phylogenetic analysis of 16S rRNA gene sequences showed that this organism represented one distinct branch within the family Sphingobacteriaceae , most closely related to the genus Mucilaginibacter . Strain M47C3BT formed a distinct lineage, closely related to Mucilaginibacter dorajii KACC 14556T, with which it shared 97.2 % 16S rRNA gene sequence similarity. The other members of the genus Mucilaginibacter included in the same clade were Mucilaginibacter lappiensis ATCC BAA-1855T sharing 97.0 % similarity and Mucilaginibacter composti TR6-03T that had a lower similarity (95.7 %). The novel strain was Gram-staining-negative, formed rod-shaped cells, grew optimally at 26 °C and at pH 7, and was able to grow with up to 0.3 % (w/v) NaCl. The respiratory quinone was menaquinone 7 (MK-7) and the major fatty acids of the strain were summed feature 3 (C16 : 1ω7c/iso-C15 : 0 2-OH), iso-C15 : 0 and iso-C17 : 0 3-OH, representing 73.5 % of the total fatty acids. The major components of the polar lipid profile of strain M47C3BT consisted of phosphatidylethanolamine, three unidentified aminophospholipids, one unidentified aminolipid and three unidentified polar lipids. The G+C content of the DNA was 40.6 mol%. On the basis of the phylogenetic analysis and physiological and biochemical characteristics we propose the name Mucilaginibacter pineti sp. nov. for the novel species represented by strain M47C3BT ( = CIP 110632T = LMG 28160T).

Chitinophaga costaii sp. nov., an endophyte of Pinus pinaster, and emended description of Chitinophaga niabensis

Bacterial strain A37T2T was isolated from the endophytic microbial community of a Pinus pinaster tree trunk and characterized. Strain A37T2T was Gram-stain-negative, formed rod-shaped cells, and grew optimally at 26–30 °C and at pH 5.5–7.5. The G+C content of the DNA was 46.6 mol%. The major respiratory quinone was menaquinone 7 (MK-7) and the major fatty acids were C16 : 1ω5c and iso-C15 : 0, representing 61.7 % of the total fatty acids. The polar lipids consisted of phosphatidylethanolamine, four unidentified aminophospholipids, one unidentified phospholipid, two unidentified aminolipids and three unidentified lipids. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain A37T2T belonged to the family Chitinophagaceae , forming a distinct branch with Chitinophaga niabensis JS13-10T within the genus Chitinophaga . Strain A37T2T shared between 92.7 and 95.1 % 16S rRNA gene sequence similarity with the type strains of species of the genus Chitinophaga . The phylogenetic, phenotypic and chemotaxonomic data presented indicate that strain A37T2T represents a novel species of the genus Chitinophaga , for which the name Chitinophaga costaii sp. nov. is proposed. The type strain is A37T2T ( = CIP 110584T = LMG 27458T). An emended description of Chitinophaga niabensis JS13-10T is also proposed.

Virulence factors and infection ability of Pseudomonas aeruginosa isolates from a hydropathic facility and respiratory infections

AIMS

To compare the virulence pool and acute infection ability of Pseudomonas aeruginosa isolates from a hydropathic facility, used to treat respiratory conditions by inhalation of untreated natural mineral water, with clinical isolates from respiratory infections.

METHODS AND RESULTS

Pseudomonas aeruginosa isolates from a hydropathic facility and from respiratory infections were typed by pulsed-field gel electrophoresis. Nonclonal representatives of each population were selected. 18 virulence-encoding genes were screened by polymerase chain reaction and statistically compared by multiple correspondence analysis. Homogeneous distribution of genes between populations but higher genetic association in aquatic isolates was observed, as well as distinct virulence pool according to location in the water system. Acute infection ability of selected isolates from each population, in Galleria mellonella model, showed lower LD50 of the majority of the hydropathic isolates and significant variations in LD50 of biofilm isolates from different equipments.

CONCLUSIONS

Hydrotherapy Ps. aeruginosa isolates present similar virulence to isolates from respiratory infections. Hydrotherapy users may be exposed to different microbiological risks when using different treatment equipments.

SIGNIFICANCE AND IMPACT OF THE STUDY

Twenty-one million people use hydropathic facilities in Europe, and the majority present risk factors to pneumonia. This study demonstrates the health risk associated with this practice. Revision of European regulations should be considered.

Nematicidal bacteria associated to pinewood nematode produce extracellular proteases

Bacteria associated with the nematode Bursaphelenchus xylophilus, a pathogen of trees and the causal agent of pine wilt disease (PWD) may play a role in the disease. In order to evaluate their role (positive or negative to the tree), strains isolated from the track of nematodes from infected Pinus pinaster trees were screened, in vitro, for their nematicidal potential. The bacterial products, from strains more active in killing nematodes, were screened in order to identify and characterize the nematicidal agent. Forty-seven strains were tested and, of these, 21 strains showed capacity to produce extracellular products with nematicidal activity. All Burkholderia strains were non-toxic. In contrast, all Serratia strains except one exhibited high toxicity. Nematodes incubated with Serratia strains showed, by SEM observation, deposits of bacteria on the nematode cuticle. The most nematicidal strain, Serratia sp. A88copa13, produced proteases in the supernatant. The use of selective inhibitors revealed that a serine protease with 70 kDa was majorly responsible for the toxicity of the supernatant. This extracellular serine protease is different phylogenetically, in size and biochemically from previously described proteases. Nematicidal assays revealed differences in nematicidal activity of the proteases to different species of Bursaphelenchus, suggesting its usefulness in a primary screen of the nematodes. This study offers the basis for further investigation of PWD and brings new insights on the role bacteria play in the defense of pine trees against B. xylophilus. Understanding all the factors involved is important in order to develop strategies to control B. xylophilus dispersion.

Diversity of bacteria associated with Bursaphelenchus xylophilus and other nematodes isolated from Pinus pinaster trees with pine wilt disease

The pinewood nematode (PWN), Bursaphelenchus xylophilus, has been thought to be the only causal agent of pine wilt disease (PWD), however, since bacteria have been suggested to play a role in PWD, it is important to know the diversity of the microbial community associated to it. This study aimed to assess the microbial community associated with B. xylophilus and with other nematodes isolated from pine trees, Pinus pinaster, with PWD from three different affected forest areas in Portugal. One hundred and twenty three bacteria strains were isolated from PWN and other nematodes collected from 14 P. pinaster. The bacteria strains were identified by comparative analysis of the 16S rRNA gene partial sequence. All except one gram-positive strain (Actinobacteria) belonged to the gram-negative Beta and Gammaproteobacteria. Most isolates belonged to the genus Pseudomonas, Burkholderia and to the family Enterobacteriaceae. Species isolated in higher percentage were Pseudomonas lutea, Yersinia intermedia and Burkholderia tuberum. The major bacterial population associated to the nematodes differed according to the forest area and none of the isolated bacterial species was found in all different forest areas. For each of the sampled areas, 60 to 100% of the isolates produced siderophores and at least 40% produced lipases. The ability to produce siderophores and lipases by most isolates enables these bacteria to have a role in plant physiological response. This research showed a high diversity of the microbial community associated with B. xylophilus and other nematodes isolated from P. pinaster with PWD.