Phytobacter spp: the emergence of a new genus of healthcare-associated Enterobacterales encoding carbapenemases in Argentina: a case series

Members of the genus Phytobacter (order Enterobacterales) are isolated from the natural environment and clinical settings. Identification of Phytobacter strains based on biochemical characteristics is complicated due to taxonomic confusion, and they are often misidentified by automated identification systems in laboratories. In this study we describe the first three clinical cases associated with Phytobacter spp. reported in Argentina. We describe the identification, the molecular analysis using whole genome sequencing and the potential clinical relevance.

Comparison of the Peel-Associated Epiphytic Bacteria of Anthocyanin-Rich "Sun Black" and Wild-Type Tomatoes under Organic and Conventional Farming

Tomatoes are among the most consumed vegetables worldwide and represent a source of health-beneficial substances. Our study represents the first investigating the peel-associated epiphytic bacteria of red and purple (anthocyanin-rich) tomatoes subjected to organic and conventional farming systems. Proteobacteria was the dominant phylum (relative abundances 79-91%) in all experimental conditions. Enterobacteriaceae represented a large fraction (39.3-47.5%) of the communities, with Buttiauxella and Atlantibacter as the most represented genera. The core microbiota was composed of 59 operational taxonomic units (OTUs), including the majority of the most abundant ones. The occurrence of the most abundant OTUs differed among the experimental conditions. OTU 1 (Buttiauxella), OTU 2 (Enterobacteriales), and OTU 6 (Bacillales) were higher in red and purple tomatoes grown under organic farming. OTU 5 (Acinetobacter) had the highest abundance in red tomatoes subjected to organic farming. OTU 3 (Atlantibacter) was among the major OTUs in red tomatoes under both farming conditions. OTU 7 (Clavibacter) and OTU 8 (Enterobacteriaceae) had abundances ≥1% only in red tomatoes grown under conventional farming. PCA and clustering analysis highlighted a high similarity between the bacterial communities of red and purple tomatoes grown under organic farming. Furthermore, the bacterial communities of purple tomatoes grown under organic farming showed the lowest diversity and evenness. This work paves the way to understand the role of nutritional superior tomato genotypes, combined with organic farming, to modulate the presence of beneficial/harmful bacteria and supply healthier foods within a sustainable agriculture.

Resolving taxonomic confusion: establishing the genus Phytobacter on the list of clinically relevant Enterobacteriaceae

Although many clinically significant strains belonging to the family Enterobacteriaceae fall into a restricted number of genera and species, there is still a substantial number of isolates that elude this classification and for which proper identification remains challenging. With the current improvements in the field of genomics, it is not only possible to generate high-quality data to accurately identify individual nosocomial isolates at the species level and understand their pathogenic potential but also to analyse retrospectively the genome sequence databases to identify past recurrences of a specific organism, particularly those originally published under an incorrect or outdated taxonomy. We propose a general use of this approach to classify further clinically relevant taxa, i.e., Phytobacter spp., that have so far gone unrecognised due to unsatisfactory identification procedures in clinical diagnostics. Here, we present a genomics and literature-based approach to establish the importance of the genus Phytobacter as a clinically relevant member of the Enterobacteriaceae family.

Exploiting endophytic microbes as micro-factories for plant secondary metabolite production

Plant secondary metabolites have significant potential applications in a wide range of pharmaceutical, food, and cosmetic industries by providing new chemistries and compounds. However, direct isolation of such compounds from plants has resulted in over-harvesting and loss of biodiversity, currently threatening several medicinal plant species to extinction. With the breakthrough report of taxol production by an endophytic fungus of Taxus brevifolia, a new era in natural product research was established. Since then, the ability of endophytic microbes to produce metabolites similar to those produced by their host plants has been discovered. The plant "endosphere" represents a rich and unique biological niche inhabited by organisms capable of producing a range of desired compounds. In addition, plants growing in diverse habitats and adverse environmental conditions represent a valuable reservoir for obtaining rare microbes with potential applications. Despite being an attractive and sustainable approach for obtaining economically important metabolites, the industrial exploitation of microbial endophytes for the production and isolation of plant secondary metabolites remains in its infancy. The present review provides an updated overview of the prospects, challenges, and possible solutions for using microbial endophytes as micro-factories for obtaining commercially important plant metabolites.Key points• Some "plant" metabolites are rather synthesized by the associated endophytes.• Challenges: Attenuation, silencing of BGCs, unculturability, complex cross-talk.• Solutions: Simulation of in planta habitat, advanced characterization methods.

Shifting the microbiome of a coral holobiont and improving host physiology by inoculation with a potentially beneficial bacterial consortium

Background

The coral microbiome plays a key role in host health by being involved in energy metabolism, nutrient cycling, and immune system formation. Inoculating coral with beneficial bacterial consortia may enhance the ability of this host to cope with complex and changing marine environments. In this study, the coral Pocillopora damicornis was inoculated with a beneficial microorganisms for corals (BMC) consortium to investigate how the coral host and its associated microbial community would respond.

Results

High-throughput 16S rRNA gene sequencing revealed no significant differences in bacterial community α-diversity. However, the bacterial community structure differed significantly between the BMC and placebo groups at the end of the experiment. Addition of the BMC consortium significantly increased the relative abundance of potentially beneficial bacteria, including the genera Mameliella and Endozoicomonas. Energy reserves and calcification rates of the coral host were also improved by the addition of the BMC consortium. Co-occurrence network analysis indicated that inoculation of coral with the exogenous BMC consortium improved the physiological status of the host by shifting the coral-associated microbial community structure.

Conclusions

Manipulating the coral-associated microbial community may enhance the physiology of coral in normal aquarium conditions (no stress applied), which may hypothetically contribute to resilience and resistance in this host.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-021-02167-5.

Sphingomonas palmae sp. nov. and Sphingomonas gellani sp. nov., endophytically associated phyllosphere bacteria isolated from economically important crop plants

In this study, two endophytic bacterial strains designated JS21-1^T and S6-262^T isolated from leaves of Elaeis guineensis and stem tissues of Jatropha curcas respectively, were subjected for polyphasic taxonomic approach. On R2A medium, colonies of strains JS21-1^T and S6-262^T are orange and yellow, respectively. Phylogenetic analyses using 16S rRNA gene sequencing and whole-genome sequences placed the strains in distinct clades but within the genus Sphingomonas. The DNA G + C content of JS21-1^T and S6-262^T were 67.31 and 66.95%, respectively. Furthermore, the average nucleotide identity and digital DNA-DNA hybridization values of strains JS21-1^T and S6-262^T with phylogenetically related Sphingomonas species were lower than 95% and 70% respectively. The chemotaxonomic studies indicated that the major cellular fatty acids of the strain JS21-1^T were summed feature 8 (C_18:1 ω7c and/or C_18:1 ω6c), C_16:0, and C_14:0 2OH; strain S6-262^T possessed summed feature 3 (C_16:1 ω7c and/or iso-C_15:0 2-OH) and summed feature 8 (C_18:1 ω6c and/or C_18:1 ω7c). The major quinone was Q10, and the unique polyamine observed was homospermidine. The polar lipid profile comprised of mixture of sphingoglycolipid, phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol and certain uncharacterised phospholipids and lipids. Based on this polyphasic evidence, strains JS21-1^T and S6-262^T represent two novel species of the genus Sphingomonas, for which the names Sphingomonas palmae sp. nov. and Sphingomonas gellani sp. nov. are proposed, respectively. The type strain of Sphingomonas palmae sp. nov. is JS21-1^T (= DSM 27348^T = KACC 17591^T) and the type strain of Sphingomonas gellani sp. nov. is S6-262^T (= DSM 27346^T =  KACC 17594^T).

Proposal for Unification of the Genus Metakosakonia and the Genus Phytobacter to a Single Genus Phytobacter and Reclassification of Metakosakonia massiliensis as Phytobacter massiliensis comb. nov

The genus Metakosakonia, as the closest phylogenetic neighbor of the genus Kosakonia within the family Enterobacteriaceae, when proposed in 2017, consisted of M. massiliensis JC163^T and Metakosakonia spp. strains CAV1151 and GT-16. The strain CAV1151 was later classified into a novel species Phytobacter ursingii. Here, we show that the strain GT-16 shares a digital DNA-DNA hybridization (DDH) similarity of 91.0% with P. diazotrophicus DSM 17806 ^T and thus also belongs to P. diazotrophicus. M. massiliensis and the strains within the genus Phytobacter formed a monophyletic cluster on a phylogenomic tree based on the core proteins of the family Enterobacteriaceae and on a phylogenetic tree based on the 16S rRNA genes. M. massiliensis and the genus Phytobacter share average amino acid identities of 86.80‒87.41% above the threshold (86%) for genus delimitation within the family Enterobacteriaceae. Moreover, they share conserved signature indels in the intracellular growth protein IgaA and the outer membrane assembly protein AsmA. Therefore, we propose to unite the genus Metakosakonia and the genus Phytobacter to a single genus. Because the genus Phytobacter was validly published earlier in 2017 than the genus Metakosakonia in 2017, the genus name Phytobacter has priority over Metakosakonia. We propose to unite the two genera under the name Phytobacter with the type species P. diazotrophicus and reclassify M. massiliensis as P. massiliensis comb. nov. In addition, the analyses of genome relatedness and phylogenomic relationship identified one potential novel species within the genus Phytobacter and three potential novel species within the genus Kosakonia.

Chitinasiproducens palmae gen. nov., sp. nov., a new member of the family Burkholderiaceae isolated from leaf tissues of oil palm (Elaeis guineensis Jacq.)

A Gram-stain-negative, aerobic, rod-shaped, leaf-associated bacterium, designated JS23T, was isolated from surface-sterilized leaf tissue of an oil palm grown in Singapore and was investigated by polyphasic taxonomy. Phylogenetic analyses based on 16S rRNA gene sequences and 180 conserved genes in the genome of several members of Burkholderiaceae revealed that strain JS23T formed a distinct evolutionary lineage independent of other taxa within the family Burkholderiaceae . The predominant ubiquinone was Q-8. The primary polar lipids were phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, and an unidentified aminophospholipid. The major fatty acids were C16 : 0, summed feature 3 (C16 : 1  ω7c /C16 : 1  ω6c) and summed feature 8 (C18 : 1  ω7c /C18 : 1  ω6c). The size of the genome is 5.36 Mbp with a DNA G+C content of 66.2 mol%. Genomic relatedness measurements such as average nucleotide identity, genome-to-genome distance and digital DNA–DNA hybridization clearly distinguished strain JS23T from the closely related genera Burkholderia , Caballeronia , Mycetohabitans , Mycoavidus , Pandoraea , Paraburkholderia , Robbsia and Trinickia . Furthermore, average amino acid identity values and the percentages of conserved proteins, 56.0–68.4 and 28.2–45.5, respectively, were well below threshold values for genus delineation and supported the assignment of JS23T to a novel genus. On the basis of the phylogenetic, biochemical, chemotaxonomic and phylogenomic evidence, strain JS23T is proposed to represent a novel species of a new genus within the family Burkholderiaceae , for which the name Chitinasiproducens palmae gen. nov., sp. nov., is proposed with the type strain of JS23T (= DSM 27307T=KACC 17592T).