The tolerance of European alder (Alnus glutinosa Gaertn.) to soil salinity can be attributed to symbiosis with microorganisms at the absorptive root level. However, it is uncertain how soil salinity ...impacts microbial recruitment in the following growing season. We describe the bacterial and fungal communities in the rhizosphere and endosphere of A. glutinosa absorptive roots at three tested sites with different salinity level. We determined the morphological diversity of ectomycorrhizal (ECM) fungi, the endophytic microbiota in the rhizosphere, and the colonization of new absorptive roots in the following growing season. While bacterial diversity in the rhizosphere was higher than that in the absorptive root endosphere, the opposite was true for fungi. Actinomycetota, Frankiales, Acidothermus sp. and Streptomyces sp. were more abundant in the endosphere than in the rhizosphere, while Actinomycetota and Acidothermus sp. dominated at saline sites compared to nonsaline sites. Basidiomycota, Thelephorales, Russulales, Helotiales, Cortinarius spp. and Lactarius spp. dominated the endosphere, while Ascomycota, Hypocreales and Giberella spp. dominated the rhizosphere. The ECM symbioses formed by Thelephorales (Thelephora, Tomentella spp.) constituted the core community with absorptive roots in the spring and further colonized new root tips during the growing season. With an increase in soil salinity, the overall fungal abundance decreased, and Russula spp. and Cortinarius spp. were not present at all. Similarly, salinity also negatively affected the average length of the absorptive root. In conclusion, the endophytic microbiota in the rhizosphere of A. glutinosa was driven by salinity and season, while the ECM morphotype community was determined by the soil fungal community present during the growing season and renewed in the spring.
Black alder (
Gaertn.) belongs to dual mycorrhizal trees, forming ectomycorrhizal (EM) and arbuscular (AM) root structures, as well as represents actinorrhizal plants that associate with ...nitrogen-fixing actinomycete
sp. We hypothesized that the unique ternary structure of symbionts can influence community structure of other plant-associated microorganisms (bacterial and fungal endophytes), particularly under seasonally changing salinity in
roots. In our study we analyzed black alder root bacterial and fungal microbiome present at two forest test sites (saline and non-saline) in two different seasons (spring and fall). The dominant type of root microsymbionts of alder were ectomycorrhizal fungi, whose distribution depended on site (salinity):
,
, and
were more abundant at the saline site.
and
(representatives of saprotrophs or endophytes) displayed the opposite tendency. Arbuscular mycorrhizal fungi belonged to Glomeromycota (orders Paraglomales and Glomales), however, they represented less than 1% of all identified fungi. Bacterial community structure depended on test site but not on season. Sequences affiliated with
,
, and
dominated at the saline site, while
and
were more abundant at the non-saline site. Moreover, genus
was observed only at the saline site. In conclusion, bacterial and fungal community structure of alder root microsymbionts and endophytes depends on five soil chemical parameters: salinity, phosphorus, pH, saturation percentage (SP) as well as total organic carbon (TOC), and seasonality does not appear to be an important factor shaping microbial communities. Ectomycorrhizal fungi are the most abundant symbionts of mature alders growing in saline soils. However, specific distribution of nitrogen-fixing
(forming root nodules) and association of arbuscular fungi at early stages of plant development should be taken into account in further studies.
Phosphorus (P) is an essential plant nutrient that can limit plant growth due to low availability in the soil. P-solubilizing bacteria in the roots and rhizosphere increase the P use efficiency of ...plants. This study addressed the impact of plant species, the level of plant association with bacteria (rhizosphere or root endophyte) and environmental factors (e.g., seasons, soil properties) on the abundance and diversity of P-solubilizing bacteria in short-rotation coppices (SRC) of willows (
Salix
spp.) for biomass production. Two willow species (
S. dasyclados
cv
. Loden and
S. schwerinii × S. viminalis cv.
Tora) grown in mono-and mixed culture plots were examined for the abundance and diversity of bacteria in the root endosphere and rhizosphere during two seasons (fall and spring) in central Sweden and northern Germany. Soil properties, such as pH and available P and N, had a significant effect on the structure of the bacterial community. Microbiome analysis and culture-based methods revealed a higher diversity of rhizospheric bacteria than endophytic bacteria. The P-solubilizing bacterial isolates belonged mainly to Proteobacteria (85%), Actinobacteria (6%) and Firmicutes (9%).
Pseudomonas
was the most frequently isolated cultivable bacterial genus from both the root endosphere and the rhizosphere. The remaining cultivable bacterial isolates belonged to the phyla
Actinobacteria
and
Firmicutes
. In conclusion, site-specific soil conditions and the level of plant association with bacteria were the main factors shaping the bacterial communities in the willow SRCs. In particular, the concentration of available P along with the total nitrogen in the soil controlled the total bacterial diversity in willow SRCs. A lower number of endophytic and rhizospheric bacteria was observed in Loden willow species compared to that of Tora and the mix of the two, indicating that mixed growth of
Salix
species promotes P-solubilizing bacterial diversity and abundance. Therefore, a mixed plant design was presented as a management option to increase the P availability for
Salix
in SRCs. This design should be tested for further species mixtures.
The use of probiotics, prebiotics and synbiotics in poultry diets beneficially stimulates the gut microbiome thus promoting the health and welfare of the animals. In this study, we analyzed 7 poultry ...probiotics (
Lactobacillus plantarum
– B1 and B4,
Lactobacillus rhamnosus
– B3,
Bifidobacterium lactis
– B2,
Carnobacterium divergens
– B5,
Propionibacterium thoenii
– B6,
Clostridium butyricum
– B7) and 12 prebiotics, differing in chemical composition and source of origin (fungi, algae, animal, etc.). The main goal of our research was to select the most promising candidates to develop synbiotic combinations. We determined the growth kinetics of all probiotics in the presence of prebiotics in a series of
in vitro
studies to select optimal combinations. Five out of seven investigated probiotics were significantly stimulated by astragalus polysaccharide, and this prebiotic was characterized in our work as the most effective. Moreover, in the case of three probiotics, B2, B3 and B4, significant growth stimulation has been found when beta-glucan, vegetable protein hydrolysate and liquid seaweed extract were supplied. Strain B1 (
L. plantarum
) was stimulated by 6 out of 12 prebiotics. The growth of B4 (
L. plantarum
) and B2 (
B. lactis
) was enhanced by prebiotics after 2 h of incubation. A high growth rate of 3.13% was observed in the case of
L. plantarum
(B4) and a 3.37% higher rate for
B. lactis
(B3), compared to the growth of probiotics in the control medium with glucose but no prebiotics. The best candidates for synbiotic combinations based on this
in vitro
work are the strains belonging to
L. plantarum
(B4),
L. rhamnosus
(B3) and
B. lactis
(B2), consistent with prebiotics such as astragalus polysaccharides and vegetable protein hydrolysate. These combinations will be subject to future
in vivo
poultry trials involving the
in ovo
microbiome modulation.
Rhizosphere and endophytic bacteria are well known producers of siderophores, organic compounds that chelate ferric iron (Fe(3+)), and therefore play an important role in plant growth promotion in ...metalliferous areas, thereby improving bioremediation processes. However, in addition to their primary function in iron mobilization, siderophores also have the capacity to chelate other heavy metals, such as Al(3+), Zn(2+), Cu(2+), Pb(2+) and Cd(2+), that can affect homeostasis and the heavy metal tolerance of microorganisms. The main goal of our study was to select the most efficient siderophore-producing bacterial strains isolated from the roots (endophytes) and rhizosphere of Betula pendula L. and Alnus glutinosa L. growing at two heavy metal contaminated sites in southern Poland. Siderophore biosynthesis of these strains in the presence of increasing concentrations of Cd(2+) (0, 0.5, 1, 2 and 3 mM) under iron-deficiency conditions was analysed using spectrophotometric chemical tests for hydroxamates, catecholates and phenolates, as well as the separation of bacterial siderophores by HPLC and characterization of their structure by UHPLC-QTOF/MS. We proved that (i) siderophore-producing bacterial strains seems to be more abundant in the rhizosphere (47%) than in root endophytes (18%); (ii) the strains most effective at siderophore synthesis belonged to the genus Streptomyces and were able to secrete three types of siderophores under Cd(2+) stress: hydroxamates, catecholates and phenolates; (iii) in general, the addition of Cd(2+) enhanced siderophore synthesis, particularly ferrioxamine B synthesis, which may indicate that siderophores play a significant role in tolerance to Cd(2+) in Streptomyces sp.
Rhizosphere and endophytic bacteria are well known producers of siderophores, organic compounds that chelate ferric iron (Fe3+), and therefore play an important role in plant growth promotion in ...metalliferous areas, thereby improving bioremediation processes. However, in addition to their primary function in iron mobilization, siderophores also have the capacity to chelate other heavy metals, such as Al3+, Zn2+, Cu2+, Pb2+ and Cd2+, that can affect homeostasis and the heavy metal tolerance of microorganisms.
The main goal of our study was to select the most efficient siderophore-producing bacterial strains isolated from the roots (endophytes) and rhizosphere of Betula pendula L. and Alnus glutinosa L. growing at two heavy metal contaminated sites in southern Poland. Siderophore biosynthesis of these strains in the presence of increasing concentrations of Cd2+ (0, 0.5, 1, 2 and 3 mM) under iron-deficiency conditions was analysed using spectrophotometric chemical tests for hydroxamates, catecholates and phenolates, as well as the separation of bacterial siderophores by HPLC and characterization of their structure by UHPLC-QTOF/MS.
We proved that (i) siderophore-producing bacterial strains seems to be more abundant in the rhizosphere (47%) than in root endophytes (18%); (ii) the strains most effective at siderophore synthesis belonged to the genus Streptomyces and were able to secrete three types of siderophores under Cd2+ stress: hydroxamates, catecholates and phenolates; (iii) in general, the addition of Cd2+ enhanced siderophore synthesis, particularly ferrioxamine B synthesis, which may indicate that siderophores play a significant role in tolerance to Cd2+ in Streptomyces sp.
•Identification and selection of the most efficient siderophore-producing bacterial strains.•Siderophore biosynthesis in the presence of increasing concentrations of Cd2+.•Analysis of different types of siderophores: hydroxamates, catecholates and phenolates.•Separation of bacterial siderophores by HPLC and characterization of their structure by UHPLC-QTOF/MS.
Alnus glutinosa
(black alder) is a mycorrhizal pioneer tree species with tolerance to high concentrations of salt in the soil and can therefore be considered to be an important tree for the ...regeneration of forests areas devastated by excessive salt. However, there is still a lack of information about the ectomycorrhizal fungi (EMF) associated with mature individuals of
A. glutinosa
growing in natural saline conditions. The main objective of this study was to test the effect of soil salinity and other physicochemical parameters on root tips colonized by EMF, as well as on the species richness and diversity of an EMF community associated with
A. glutinosa
growing in natural conditions. We identified a significant effect of soil salinity (expressed as electrical conductivity: EC
e
and EC
1:5
) on fungal taxa but not on the total level of EM fungal colonization on roots. Increasing soil salinity promoted dark-coloured EMF belonging to the order Thelephorales (
Tomentella
sp. and
Thelephora
sp.). These fungi are also commonly found in soils polluted with heavy-metal. The ability of these fungi to grow in contaminated soil may be due to the presence of melanine, a natural dark pigment and common wall component of the Thelephoraceae that is known to act as a protective interface between fungal metabolism and biotic and abiotic environmental stressors. Moreover, increased colonization of fungi belonging to the class of Leotiomycetes and Sordiomycetes, known as endophytic fungal species, was observed at the test sites, that contained a larger content of total phosphorus. This observation confirms the ability of commonly known endophytic fungi to form ectomycorrhizal structures on the roots of
A. glutinosa
under saline stress conditions.
The tolerance of European alder (Alnusglutinosa Gaertn.) to soil salinity can be attributed to symbiosis with microorganisms at the absorptive root level. However, it is uncertain how soil salinity ...impacts microbial recruitment in the following growing season. We describe the bacterial and fungal communities in the rhizosphere and endosphere of A.glutinosa absorptive roots at three tested sites with different salinity level. We determined the morphological diversity of ectomycorrhizal (ECM) fungi, the endophytic microbiota in the rhizosphere, and the colonization of new absorptive roots in the following growing season. While bacterial diversity in the rhizosphere was higher than that in the absorptive root endosphere, the opposite was true for fungi. Actinomycetota, Frankiales, Acidothermus sp. and Streptomyces sp. were more abundant in the endosphere than in the rhizosphere, while Actinomycetota and Acidothermus sp. dominated at saline sites compared to nonsaline sites. Basidiomycota, Thelephorales, Russulales, Helotiales, Cortinarius spp. and Lactarius spp. dominated the endosphere, while Ascomycota, Hypocreales and Giberella spp. dominated the rhizosphere. The ECM symbioses formed by Thelephorales (Thelephora, Tomentella spp.) constituted the core community with absorptive roots in the spring and further colonized new root tips during the growing season. With an increase in soil salinity, the overall fungal abundance decreased, and Russula spp. and Cortinarius spp. were not present at all. Similarly, salinity also negatively affected the average length of the absorptive root. In conclusion, the endophytic microbiota in the rhizosphere of A.glutinosa was driven by salinity and season, while the ECM morphotype community was determined by the soil fungal community present during the growing season and renewed in the spring.
Saline stress is one of the most important abiotic factors limiting the growth and development of plants and associated microorganisms. While the impact of salinity on associations of arbuscular ...fungi is relatively well understood, knowledge of the ectomycorrhizal (EM) fungi of trees growing on saline land is limited. The main objective of this study was to determine the density and diversity of EM fungi associated with three tree species,
Salix alba
,
Salix caprea
and
Betula pendula
, growing in saline soil during two seasons, autumn and spring. The site was located in central Poland, and the increased salinity of the soil was of anthropogenic origin from soda production. The degree of EM colonisation of fine root tips varied between 9 and 34 % and depended on the tree species of interest (
S. caprea
<
S. alba
<
B. pendula
) and season (spring < autumn). Moreover, the ectomycorrhizal colonisation of
B. pendula
was positively correlated with pH and CaCO
3
, while for
S. caprea
and
S. alba,
colonisation was associated with most of the other soil parameters investigated; e.g. salinity, C
org
and N. Analysis of EM fungi revealed four to five different morphotypes per each season:
Tomentella
sp. Sa-A,
Hebeloma collariatum
Sc-A,
Geopora
sp. Sc-A,
Helotiales
sp. Bp-A in the autumn and
Tomentella
sp. Sa-S,
Tomentella
sp. Sc-S and three morphotypes from the families Thelephoraceae and Pyronemataceae in the spring. In conclusion, the density of EM is related to the level of salinity (EC
e
), season and tree species.
Tomentella
spp.,
Hebeloma
sp.,
Geopora
sp. and
Helotiales
sp. are groups of species highly adapted to saline conditions.
•Icelandic biocrusts were P-rich though microbial P constituted <0.2% of total P.•Moderately labile P was predominant in biocrusts across the sites.•Eukaryotic microalgae including diatoms dominated ...Icelandic biocrusts.•Cyanobacteria in the biocrusts were mostly filamentous forms.•Majority of fungi isolated from the biocrusts belonged to Ascomycota and Mucoromycota.
Icelandic biocrusts are unique micro-ecosystems, considering their origin from volcanic material as a mineral base. However, little is known about their chemistry and diversity of microorganisms. Being phosphorus (P)-rich, Icelandic soils contribute to the global P cycling. Therefore, here, we focused on investigating P content, P pools, microbial biomass P (Pmic) and potential phosphatase activity along an altitude gradient (11–157 m a.s.l.) stretching away from the sea coast. Total P (Ptotal) content in the studied biocrusts and soils varied between 982 and 1571 mg kg−1 and Pmic, measured in biocrusts, constituted only a minor fraction <0.2% of Ptotal. Sequential P fractionation revealed the dominance of moderately labile P in biocrusts across the sites. Additionally, basic physicochemical properties were measured in biocrusts, and contents of total carbon (TC) and total nitrogen (TN) were positively correlated to Pmic and potential phosphatase activity.
Diversity and abundance of microbial phototrophs in the studied biocrusts were assessed by morphological observations using light and epifluorescence microscopy. Microphototrophic communities were dominated by eukaryotic microalgae (e.g. Chlorella, Coccomyxa, Stichococcus) including diatoms (e.g. Pinnularia and Eunotia) and the highest cell biovolume was recorded in the site located at the sea coast. Furthermore, the majority of cyanobacteria belonged to filamentous forms, such as Microcoleus, Leptolyngbya, Phormidesmis and Stenomitos. In addition, the majority of fungal strains isolated from the studied biocrusts belonged to Ascomycota (e.g. Penicillium, Fusarium, Truncatella) and Zygomycota (e.g. Mucor, Mortierella).
Overall, this study provides for the first time a comprehensive description of microbial community composition and P distribution in Icelandic biocrusts, which were previously overlooked.
PDF
