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Plants (Basel, Switzerland) Sep 2023The role of Calcium ions (Ca) is extensively documented and comprehensively understood in eukaryotic organisms. Nevertheless, emerging insights, primarily derived from... (Review)
Review
The role of Calcium ions (Ca) is extensively documented and comprehensively understood in eukaryotic organisms. Nevertheless, emerging insights, primarily derived from studies on human pathogenic bacteria, suggest that this ion also plays a pivotal role in prokaryotes. In this review, our primary focus will be on unraveling the intricate Ca toolkit within prokaryotic organisms, with particular emphasis on its implications for plant growth-promoting rhizobacteria (PGPR). We undertook an in silico exploration to pinpoint and identify some of the proteins described in the existing literature, including prokaryotic Ca channels, pumps, and exchangers that are responsible for regulating intracellular Calcium concentration ([Ca]), along with the Calcium-binding proteins (CaBPs) that play a pivotal role in sensing and transducing this essential cation. These investigations were conducted in four distinct PGPR strains: subsp. SMMP3, SVBP6, sp. BP01, and sp. 2A, which have been isolated and characterized within our research laboratories. We also present preliminary experimental data to evaluate the influence of exogenous Ca concentrations ([Ca]) on the growth dynamics of these strains.
PubMed: 37836138
DOI: 10.3390/plants12193398 -
Microbiome Mar 2020Methanol is the second most abundant volatile organic compound in the atmosphere, with the majority produced as a metabolic by-product during plant growth. There is a...
BACKGROUND
Methanol is the second most abundant volatile organic compound in the atmosphere, with the majority produced as a metabolic by-product during plant growth. There is a large disparity between the estimated amount of methanol produced by plants and the amount which escapes to the atmosphere. This may be due to utilisation of methanol by plant-associated methanol-consuming bacteria (methylotrophs). The use of molecular probes has previously been effective in characterising the diversity of methylotrophs within the environment. Here, we developed and applied molecular probes in combination with stable isotope probing to identify the diversity, abundance and activity of methylotrophs in bulk and in plant-associated soils.
RESULTS
Application of probes for methanol dehydrogenase genes (mxaF, xoxF, mdh2) in bulk and plant-associated soils revealed high levels of diversity of methylotrophic bacteria within the bulk soil, including Hyphomicrobium, Methylobacterium and members of the Comamonadaceae. The community of methylotrophic bacteria captured by this sequencing approach changed following plant growth. This shift in methylotrophic diversity was corroborated by identification of the active methylotrophs present in the soils by DNA stable isotope probing using C-labelled methanol. Sequencing of the 16S rRNA genes and construction of metagenomes from the C-labelled DNA revealed members of the Methylophilaceae as highly abundant and active in all soils examined. There was greater diversity of active members of the Methylophilaceae and Comamonadaceae and of the genus Methylobacterium in plant-associated soils compared to the bulk soil. Incubating growing pea plants in a CO atmosphere revealed that several genera of methylotrophs, as well as heterotrophic genera within the Actinomycetales, assimilated plant exudates in the pea rhizosphere.
CONCLUSION
In this study, we show that plant growth has a major impact on both the diversity and the activity of methanol-utilising methylotrophs in the soil environment, and thus, the study contributes significantly to efforts to balance the terrestrial methanol and carbon cycle. Video abstract.
Topics: Alcohol Oxidoreductases; Bacteria; DNA, Bacterial; Genetic Variation; Metagenome; Methanol; Methylobacterium; Phylogeny; Plant Physiological Phenomena; Plants; RNA, Ribosomal, 16S; Rhizosphere; Soil Microbiology
PubMed: 32156318
DOI: 10.1186/s40168-020-00801-4 -
BMC Microbiology Nov 2020To explore the optimum fermentation conditions for tobacco leaves and also screen the microbiota and metabolites that are beneficial for fermentation.
BACKGROUND
To explore the optimum fermentation conditions for tobacco leaves and also screen the microbiota and metabolites that are beneficial for fermentation.
METHODS
Tobacco leaves were fermented at 25 °C, 35 °C, and 45 °C for 2, 4, and 6 weeks, respectively. For identification of the best fermentation temperature, physicochemical properties and sensory quality of fermented tobacco were investigated. Subsequently, based on the appropriate temperature, 16 s rRNA sequencing and metabolomics analysis of tobacco were performed to monitor the change of microbes and metabolites during fermentation process (from 2 to 6 weeks).
RESULTS
Sensory quality analysis indicated that fermentation at 45 °C for 6 weeks represented the optimum condition. Metabolomics analysis showed that a total of 415 metabolites were annotated. The increase of fermentation period led to significant changes of metabolites. Results revealed an increase in concentration of L-phenylalanine and sphingosine as well as decreased concentration of betaine and phytosphingosine with the prolongation of fermentation period (2 to 6 weeks). Distinct changes in the microbiota were also observed with prolongation of the fermentation time. Results revealed that Pseudomonas, Pantoea, and Burkholderia were dominant bacteria in fermentation at 45 °C for 6 weeks. With the extension of the fermentation time, the abundance of Pseudomonas increased, while that of Sphingomonas and Methylobacterium decreased. Furthermore, microbiota profiles were tightly relevant to the altered metabolites, especially compounds involved in the sphingolipid metabolism.
CONCLUSION
Suitable fermentation conditions were 45 °C for 6 weeks; phytosphingosine and sphingosine might affect tobacco fermentation via the sphingolipid metabolism pathway. This study provides a theoretical basis for guiding tobacco fermentation and gives insights into reducing harmful substances during tobacco fermentation.
Topics: Bacteria; Fermentation; Microbiota; Plant Leaves; RNA, Ribosomal, 16S; Sensation; Sphingolipids; Temperature; Time Factors; Nicotiana
PubMed: 33213368
DOI: 10.1186/s12866-020-02035-8 -
Scientific Reports Feb 2023Malignant pleural effusions (MPE) complicate malignancies and portend worse outcomes. MPE is comprised of various components, including immune cells, cancer cells, and...
Malignant pleural effusions (MPE) complicate malignancies and portend worse outcomes. MPE is comprised of various components, including immune cells, cancer cells, and cell-free DNA/RNA. There have been investigations into using these components to diagnose and prognosticate MPE. We hypothesize that the microbiome of MPE is unique and may be associated with diagnosis and prognosis. We compared the microbiota of MPE against microbiota of pleural effusions from non-malignant and paramalignant states. We collected a total of 165 pleural fluid samples from 165 subjects; Benign (n = 16), Paramalignant (n = 21), MPE-Lung (n = 57), MPE-Other (n = 22), and Mesothelioma (n = 49). We performed high throughput 16S rRNA gene sequencing on pleural fluid samples and controls. We showed that there are compositional differences among pleural effusions related to non-malignant, paramalignant, and malignant disease. Furthermore, we showed differential enrichment of bacterial taxa within MPE depending on the site of primary malignancy. Pleural fluid of MPE-Lung and Mesothelioma were associated with enrichment with oral and gut bacteria that are commonly thought to be commensals, including Rickettsiella, Ruminococcus, Enterococcus, and Lactobacillales. Mortality in MPE-Lung is associated with enrichment in Methylobacterium, Blattabacterium, and Deinococcus. These observations lay the groundwork for future studies that explore host-microbiome interactions and their influence on carcinogenesis.
Topics: Humans; RNA, Ribosomal, 16S; Pleural Effusion, Malignant; Mesothelioma; Biomarkers; Pleural Effusion; Mesothelioma, Malignant; Prognosis; Microbiota; Lung Neoplasms
PubMed: 36755121
DOI: 10.1038/s41598-023-29001-4 -
Microbiology Spectrum Jun 2023The Amazon River basin sustains dramatic hydrochemical gradients defined by three water types: white, clear, and black waters. In black water, important loads of...
The Amazon River basin sustains dramatic hydrochemical gradients defined by three water types: white, clear, and black waters. In black water, important loads of allochthonous humic dissolved organic matter (DOM) result from the bacterioplankton degradation of plant lignin. However, the bacterial taxa involved in this process remain unknown, since Amazonian bacterioplankton has been poorly studied. Its characterization could lead to a better understanding of the carbon cycle in one of the Earth's most productive hydrological systems. Our study characterized the taxonomic structure and functions of Amazonian bacterioplankton to better understand the interplay between this community and humic DOM. We conducted a field sampling campaign comprising 15 sites distributed across the three main Amazonian water types (representing a gradient of humic DOM), and a 16S rRNA metabarcoding analysis based on bacterioplankton DNA and RNA extracts. Bacterioplankton functions were inferred using 16S rRNA data in combination with a tailored functional database from 90 Amazonian basin shotgun metagenomes from the literature. We discovered that the relative abundances of fluorescent DOM fractions (humic-, fulvic-, and protein-like) were major drivers of bacterioplankton structure. We identified 36 genera for which the relative abundance was significantly correlated with humic DOM. The strongest correlations were found in the Polynucleobacter, Methylobacterium, and Acinetobacter genera, three low abundant but omnipresent taxa that possessed several genes involved in the main steps of the β-aryl ether enzymatic degradation pathway of diaryl humic DOM residues. Overall, this study identified key taxa with DOM degradation genomic potential, the involvement of which in allochthonous Amazonian carbon transformation and sequestration merits further investigation. The Amazon basin discharge carries an important load of terrestrially derived dissolved organic matter (DOM) to the ocean. The bacterioplankton from this basin potentially plays important roles in transforming this allochthonous carbon, which has consequences on marine primary productivity and global carbon sequestration. However, the structure and function of Amazonian bacterioplanktonic communities remain poorly studied, and their interactions with DOM are unresolved. In this study, we (i) sampled bacterioplankton in all the main Amazon tributaries, (ii) combined information from the taxonomic structure and functional repertory of Amazonian bacterioplankton communities to understand their dynamics, (iii) identified the main physicochemical parameters shaping bacterioplanktonic communities among a set of >30 measured environmental parameters, and (iv) characterized how bacterioplankton structure varies according to the relative abundance of humic compounds, a by-product from the bacterial degradation process of allochthonous DOM.
Topics: Water; Dissolved Organic Matter; RNA, Ribosomal, 16S; Aquatic Organisms; Carbon
PubMed: 37199657
DOI: 10.1128/spectrum.04793-22 -
PloS One 2017Hopanoids are sterol-like membrane lipids widely used as geochemical proxies for bacteria. Currently, the physiological role of hopanoids is not well understood, and...
Hopanoids are sterol-like membrane lipids widely used as geochemical proxies for bacteria. Currently, the physiological role of hopanoids is not well understood, and this represents one of the major limitations in interpreting the significance of their presence in ancient or contemporary sediments. Previous analyses of mutants lacking hopanoids in a range of bacteria have revealed a range of phenotypes under normal growth conditions, but with most having at least an increased sensitivity to toxins and osmotic stress. We employed hopanoid-free strains of Methylobacterium extorquens DM4, uncovering severe growth defects relative to the wild-type under many tested conditions, including normal growth conditions without additional stressors. Mutants overproduce carotenoids-the other major isoprenoid product of this strain-and show an altered fatty acid profile, pronounced flocculation in liquid media, and lower growth yields than for the wild-type strain. The flocculation phenotype can be mitigated by addition of cellulase to the medium, suggesting a link between the function of hopanoids and the secretion of cellulose in M. extorquens DM4. On solid media, colonies of the hopanoid-free mutant strain were smaller than wild-type, and were more sensitive to osmotic or pH stress, as well as to a variety of toxins. The results for M. extorquens DM4 are consistent with the hypothesis that hopanoids are important for membrane fluidity and lipid packing, but also indicate that the specific physiological processes that require hopanoids vary across bacterial lineages. Our work provides further support to emerging observations that the role of hopanoids in membrane robustness and barrier function may be important across lineages, possibly mediated through an interaction with lipid A in the outer membrane.
Topics: Carotenoids; Cell Membrane; Cellulase; Culture Media; Fatty Acids; Flocculation; Hydrogen-Ion Concentration; Membrane Fluidity; Membrane Lipids; Methylobacterium extorquens; Mutation; Osmolar Concentration; Stress, Physiological
PubMed: 28319163
DOI: 10.1371/journal.pone.0173323 -
Microbiology Spectrum Feb 2023Wild rice has been demonstrated to possess enriched genetic diversity and multiple valuable traits involved in disease/pest resistance and abiotic stress tolerance,...
Wild rice has been demonstrated to possess enriched genetic diversity and multiple valuable traits involved in disease/pest resistance and abiotic stress tolerance, which provides a potential resource for sustainable agriculture. However, unlike the plant compartments such as rhizosphere, the structure and assembly of phyllosphere microbial communities of wild rice remain largely unexplored. Through amplicon sequencing, this study compared the phyllosphere bacterial and fungal communities of wild rice and its neighboring cultivated rice. The core phyllosphere microbial taxa of both wild and cultivated rice are dominated with , , , and , which are potentially beneficial to rice growth and health. Compared to the cultivated rice, , , , and were significantly enriched in the wild rice phyllosphere. The potentially nitrogen-fixing is the dominated wild-enriched microbe; is the hub taxon of wild rice networks. In addition, the microbiota of wild rice was more governed by deterministic assembly with a more complicated and stable community network than the cultivated rice. Our study provides a list of the beneficial microbes in the wild rice phyllosphere and reveals the microbial divergence between wild rice and cultivated rice in the original habitats, which highlights the potential selective role of wild rice in recruiting specific microbiomes for enhancing crop performance and promoting sustainable food production. Plant microbiota are being considered a lever to increase the sustainability of food production under a changing climate. In particular, the microbiomes associated with ancestors of modern cultivars have the potential to support their domesticated cultivars. However, few efforts have been devoted to studying the biodiversity and functions of microbial communities in the native habitats of ancestors of modern crop species. This study provides a list of the beneficial microbes in the wild rice phyllosphere and explores the microbial interaction patterns and the functional profiles of wild rice. This information could be useful for the future utilization of the plant microbiome to enhance crop performance and sustainability, especially in the framework of sustainable agroecosystems.
Topics: Oryza; Microbiota; Bacteria; Mycobiome; Basidiomycota
PubMed: 36625666
DOI: 10.1128/spectrum.04371-22 -
Bioresource Technology May 2022In the context of algal wastewater bioremediation, this study has identified a novel consortium formed by the bacterium Methylobacterium oryzae and the microalga...
In the context of algal wastewater bioremediation, this study has identified a novel consortium formed by the bacterium Methylobacterium oryzae and the microalga Chlamydomonas reinhardtii that greatly increase biomass generation (1.22 g L·d), inorganic nitrogen removal (>99%), and hydrogen production (33 mL·L) when incubated in media containing ethanol and methanol. The key metabolic aspect of this relationship relied on the bacterial oxidation of ethanol to acetate, which supported heterotrophic algal growth. However, in the bacterial monocultures the acetate accumulation inhibited bacterial growth. Moreover, in the absence of methanol, ethanol was an unsuitable carbon source and its incomplete oxidation to acetaldehyde had a toxic effect on both the alga and the bacterium. In cocultures, both alcohols were used as carbon sources by the bacteria, the inhibitory effects were overcome and both microorganisms mutually benefited. Potential biotechnological applications in wastewater treatment, biomass generation and hydrogen production are discussed.
Topics: Acetates; Biomass; Carbon; Chlamydomonas; Denitrification; Ethanol; Hydrogen; Methanol; Methylobacterium; Nitrogen
PubMed: 35364237
DOI: 10.1016/j.biortech.2022.127088 -
Frontiers in Microbiology 2021Microorganisms are ubiquitous in the environment, and the atmosphere is no exception. However, airborne bacterial communities are some of the least studied. Increasing...
Microorganisms are ubiquitous in the environment, and the atmosphere is no exception. However, airborne bacterial communities are some of the least studied. Increasing our knowledge about these communities and how environmental factors shape them is key to understanding disease outbreaks and transmission routes. We describe airborne bacterial communities at two different sites in Tenerife, La Laguna (urban, 600 m.a.s.l.) and Izaña (high mountain, 2,400 m.a.s.l.), and how they change throughout the year. Illumina MiSeq sequencing was used to target 16S rRNA genes in 293 samples. Results indicated a predominance of Proteobacteria at both sites (>65%), followed by Bacteroidetes, Actinobacteria, and Firmicutes. Gammaproteobacteria were the most frequent within the Proteobacteria phylum during spring and winter, while Alphaproteobacteria dominated in the fall and summer. Within the 519 genera identified, was the most frequent during spring (35.75%) and winter (30.73%); (24.49%) and (19.88%) dominated in the summer; and represented 10.26 and 12.41% of fall and winter samples, respectively. was also identified in 17.15% of the fall samples. These five genera were more abundant at the high mountain site, while other common airborne bacteria were more frequent at the urban site (, , , and ). Diversity values showed different patterns for both sites, with higher values during the cooler seasons in Izaña, whereas the opposite was observed in La Laguna. Regarding wind back trajectories, Tropical air masses were significantly different from African ones at both sites, showing the highest diversity and characterized by genera regularly associated with humans (, , and ), as well as others related to extreme conditions () or typically associated with animals (Lachnospiraceae). Marine and African air masses were consistent and very similar in their microbial composition. By contrast, European trajectories were dominated by , , , and . These data contribute to our current state of knowledge in the field of atmospheric microbiology. However, future studies are needed to increase our understanding of the influence of different environmental factors on atmospheric microbial dispersion and the potential impact of airborne microorganisms on ecosystems and public health.
PubMed: 34737729
DOI: 10.3389/fmicb.2021.732961 -
BMC Microbiology Feb 2022Symbiotic Methylobacterium strains comprise a significant part of plant microbiomes. Their presence enhances plant productivity and stress resistance, prompting...
BACKGROUND
Symbiotic Methylobacterium strains comprise a significant part of plant microbiomes. Their presence enhances plant productivity and stress resistance, prompting classification of these strains as plant growth-promoting bacteria (PGPB). Methylobacteria can synthesize unusually high levels of plant hormones, called cytokinins (CKs), including the most active form, trans-Zeatin (tZ).
RESULTS
This study provides a comprehensive inventory of 46 representatives of Methylobacterium genus with respect to phytohormone production in vitro, including 16 CK forms, abscisic acid (ABA) and indole-3-acetic acid (IAA). High performance-liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) analyses revealed varying abilities of Methylobacterium strains to secrete phytohormones that ranged from 5.09 to 191.47 pmol mL for total CKs, and 0.46 to 82.16 pmol mL for tZ. Results indicate that reduced methanol availability, the sole carbon source for bacteria in the medium, stimulates CK secretion by Methylobacterium. Additionally, select strains were able to transform L-tryptophan into IAA while no ABA production was detected.
CONCLUSIONS
To better understand features of CKs in plants, this study uncovers CK profiles of Methylobacterium that are instrumental in microbe selection for effective biofertilizer formulations.
Topics: Chromatography, High Pressure Liquid; Cytokinins; Methylobacterium; Tandem Mass Spectrometry
PubMed: 35135483
DOI: 10.1186/s12866-022-02454-9