Forest Soil Bacteria: Diversity, Involvement in Ecosystem Processes, and Response to Global Change

SUMMARY The ecology of forest soils is an important field of research due to the role of forests as carbon sinks. Consequently, a significant amount of information has been accumulated concerning their ecology, especially for temperate and boreal forests. Although most studies have focused on fungi, forest soil bacteria also play important roles in this environment. In forest soils, bacteria inhabit multiple habitats with specific properties, including bulk soil, rhizosphere, litter, and deadwood habitats, where their communities are shaped by nutrient availability and biotic interactions. Bacteria contribute to a range of essential soil processes involved in the cycling of carbon, nitrogen, and phosphorus. They take part in the decomposition of dead plant biomass and are highly important for the decomposition of dead fungal mycelia. In rhizospheres of forest trees, bacteria interact with plant roots and mycorrhizal fungi as commensalists or mycorrhiza helpers. Bacteria also mediate multiple critical steps in the nitrogen cycle, including N fixation. Bacterial communities in forest soils respond to the effects of global change, such as climate warming, increased levels of carbon dioxide, or anthropogenic nitrogen deposition. This response, however, often reflects the specificities of each studied forest ecosystem, and it is still impossible to fully incorporate bacteria into predictive models. The understanding of bacterial ecology in forest soils has advanced dramatically in recent years, but it is still incomplete. The exact extent of the contribution of bacteria to forest ecosystem processes will be recognized only in the future, when the activities of all soil community members are studied simultaneously.

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The effect of inoculation of pea plants with mycorrhizal fungi and Rhizobium on nitrogen and phosphorus assimilation

Plant Soil and Environment ◽

10.17221/3463-pse ◽

2011 ◽

Vol 52 (No. 10) ◽

pp. 435-440 ◽

Cited By ~ 27

Author(s):

M. Geneva ◽

G. Zehirov ◽

E. Djonova ◽

N. Kaloyanova ◽

G. Georgiev ◽

...

Keyword(s):

Nitrogen Fixation ◽

Mycorrhizal Fungi ◽

Glomus Mosseae ◽

Rhizobium Leguminosarum ◽

Glomus Intraradices ◽

Plant Biomass ◽

Phosphorus Level ◽

Nitrogen And Phosphorus ◽

Nitrogen Fixation Activity ◽

Fixation Activity

The study evaluated the response of pea (Pisum sativum cv. Avola) to arbuscular mycorrhizal fungi (AM) species Glomus mosseae and Glomus intraradices and Rhizobium leguminosarum bv. viceae, strain D 293, regarding the growth, photosynthesis, nodulation and nitrogen fixation activity. Pea plants were grown in a glasshouse until the flowering stage (35 days), in 4 kg plastic pots using leached cinnamonic forest soil (Chromic Luvisols – FAO) at P levels 13.2 (P1) and 39.8 (P2) mg P/kg soil. The obtained results demonstrated that the dual inoculation of pea plants significantly increased the plant biomass, photosynthetic rate, nodulation, and nitrogen fixation activity in comparison with single inoculation with Rhizobium leguminosarum bv. viceae strain D 293. On the other hand, coinoculation significantly increased the total phosphorus content in plant tissue, acid phosphatase activity and percentage of root colonization. The effectiveness of coinoculation with Rhizobium leguminosarum and Glomus mosseae was higher at the low phosphorus level while the coinoculation with Glomus intraradices appeared to be the most effective at higher phosphorus level.

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Effects of Fire on the Growth, Nutrient Content and Rate of Nitrogen Fixation of the Cycad Macrozamia riedlei

Australian Journal of Botany ◽

10.1071/bt9800271 ◽

1980 ◽

Vol 28 (3) ◽

pp. 271 ◽

Cited By ~ 58

Author(s):

TS Grove ◽

AM O'connell ◽

N Malajczuk

Keyword(s):

Nitrogen Fixation ◽

Forest Ecosystem ◽

Plant Biomass ◽

Nitrogenase Activity ◽

Leaf Growth ◽

Nutrient Content ◽

Nitrogen And Phosphorus ◽

Eucalyptus Marginata ◽

Plant Parts ◽

Coralloid Roots

The response of Macrozamia riedlei(Gaud.) C.A. Gardn. to fire, and its contribution to the input of nitrogen to the jarrah (Eucalyptus marginata Donn ex Sm.) forest ecosystem of south-western Australia, were studied by measuring the biomass and nutrient content of plant parts, and the nitrogenase activity of coralloid roots, in relation to time since burning. Leaf growth was rapid during the first year following fire. In forest burnt 1-5 years previously, the ratio of weight of leaves to weight of bole did not differ significantly between sites. On a site burnt 7 years previously a reduced proportion of leaves in the total plant biomass was attributed to a yellowing and senescence of leaves. The ratio of weight of coralloid roots to weight of boles was greatest on the most recently burnt site. Concentrations of nitrogen and phosphorus in leaves, and phosphorus, potassium and zinc in coralloid roots, were significantly higher in plants growing in recently burnt forest. Concentrations of calcium, sodium and chlorine in leaves were higher on sites which had not been burnt recently. The rate of acetylene reduction, expressed per unit of bole weight, was greatest where forest had been burnt 1 year before sampling and decreased to a minimum where burning had occurred 7 years previously. This trend resulted from a decrease in both the weight and nitrogenase activity of coralloid roots with increasing time since burning. Estimated rates of nitrogen fixation were 8.4 and 1.4 kg ha-1 year-1 on sites burnt 1 . 5 and 7 years previously. In the period between successive prescribed burns (5 to 7 years), M. riedlei was estimated to fix c. 35 kg nitrogen ha-1. This appears to be a significant input in relation to the nitrogen balance of the jarrah forest ecosystem.

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Microplastic fiber and drought effects on plants and soil are only slightly modified by arbuscular mycorrhizal fungi

Soil Ecology Letters ◽

10.1007/s42832-020-0060-4 ◽

2020 ◽

Author(s):

Anika Lehmann ◽

Eva F. Leifheit ◽

Linshan Feng ◽

Joana Bergmann ◽

Anja Wulf ◽

...

Keyword(s):

Global Change ◽

Mycorrhizal Fungi ◽

Plant Biomass ◽

Soil Aggregates ◽

Arbuscular Mycorrhizal ◽

Am Fungi ◽

Soil System ◽

Plant Soil ◽

Greenhouse Study ◽

Drought Conditions

Abstract Microplastics are increasingly recognized as a factor of global change. By altering soil inherent properties and processes, ripple-on effects on plants and their symbionts can be expected. Additionally, interactions with other factors of global change, such as drought, can influence the effect of microplastics. We designed a greenhouse study to examine effects of polyester microfibers, arbuscular mycorrhizal (AM) fungi and drought on plant, microbial and soil responses. We found that polyester microfibers increased the aboveground biomass of Allium cepa under well-watered and drought conditions, but under drought conditions the AM fungal-only treatment reached the highest biomass. Colonization with AM fungi increased under microfiber contamination, however, plant biomass did not increase when both AM fungi and fibers were present. The mean weight diameter of soil aggregates increased with AM fungal inoculation overall but decreased when the system was contaminated with microfibers or drought stressed. Our study adds additional support to the mounting evidence that microplastic fibers in soil can affect the plant-soil system by promoting plant growth, and favoring key root symbionts, AM fungi. Although soil aggregation is usually positively influenced by plant roots and AM fungi, and microplastic promotes both, our results show that plastic still had a negative effect on soil aggregates. Even though there are concerns that microplastic might interact with other factors of global change, our study revealed no such effect for drought.

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Physiological and transcriptomic response of Medicago truncatula to high and low benefit mycorrhizal fungi

10.1101/2020.12.11.421693 ◽

2020 ◽

Author(s):

Kevin R. Cope ◽

Arjun Kafle ◽

Jaya Krishna Yakha ◽

Philip E. Pfeffer ◽

Gary D. Strahan ◽

...

Keyword(s):

Medicago Truncatula ◽

Mycorrhizal Fungi ◽

Host Plants ◽

Molecular Mechanisms ◽

Plant Biomass ◽

Arbuscular Mycorrhizal ◽

Defense Responses ◽

Ammonium Transporter ◽

Nitrogen And Phosphorus ◽

Transcriptomic Response

Arbuscular mycorrhizal (AM) fungi provide their host plants with greater access to limited mineral nutrients, but the amount they provide can be variable. Here, we evaluated the capacity of the high-benefit fungus Rhizophagus irregularis 09 and the low-benefit fungus Glomus aggregatum 165 to transfer nitrogen and phosphorus to the host plant Medicago truncatula, and identified putative molecular mechanisms regulating the physiological response of the host to these fungi. R. irregularis led to an increase in plant biomass and transferred more nitrogen and phosphate to the host than G. aggregatum. This increase was linked to elevated expression of known mycorrhiza-induced phosphate (PT8), ammonium (AMT2;3), and nitrate (NPF4.12) transporters in the roots, as well as the putative ammonium transporter NIP1;5. R. irregularis also stimulated the expression of photosynthesis related genes in the shoot and the upregulation of the mycorrhiza-induced sugar transporter SWEET1.2 and the lipid biosynthesis gene RAM2 in the roots, which is indicative of increased carbon flux to this fungus. In contrast, G. aggregatum induced biotic stress defense response genes (e.g., Medtr4g120760 and Medtr8g096900) in the shoots, and several genes associated with the GO term "response to water deprivation" in the roots of M. truncatula. This could indicate that the host perceives colonization by the low-benefit fungus as pathogen attack, or that G. aggregatum is more effective than R. irregularis at priming host defense responses. Our findings reveal novel insights into the molecular mechanisms by which host plants reward high- but sanction low-benefit arbuscular mycorrhizal symbionts.

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Physiological and biochemical responses of soybean plants inoculated with Arbuscular mycorrhizal fungi and Bradyrhizobium under drought stress

BMC Plant Biology ◽

10.1186/s12870-021-02949-z ◽

2021 ◽

Vol 21 (1) ◽

Author(s):

Mohamed S. Sheteiwy ◽

Dina Fathi Ismail Ali ◽

You-Cai Xiong ◽

Marian Brestic ◽

Milan Skalicky ◽

...

Keyword(s):

Drought Stress ◽

Arbuscular Mycorrhizal Fungi ◽

Secondary Metabolism ◽

Mycorrhizal Fungi ◽

Plant Biomass ◽

Arbuscular Mycorrhizal ◽

Growth And Yield ◽

Relative Expression ◽

Reverse Trend ◽

Soybean Plants

Abstract Background The present study aims to study the effects of biofertilizers potential of Arbuscular Mycorrhizal Fungi (AMF) and Bradyrhizobium japonicum (B. japonicum) strains on yield and growth of drought stressed soybean (Giza 111) plants at early pod stage (50 days from sowing, R3) and seed development stage (90 days from sowing, R5). Results Highest plant biomass, leaf chlorophyll content, nodulation, and grain yield were observed in the unstressed plants as compared with water stressed-plants at R3 and R5 stages. At soil rhizosphere level, AMF and B. japonicum treatments improved bacterial counts and the activities of the enzymes (dehydrogenase and phosphatase) under well-watered and drought stress conditions. Irrespective of the drought effects, AMF and B. japonicum treatments improved the growth and yield of soybean under both drought (restrained irrigation) and adequately-watered conditions as compared with untreated plants. The current study revealed that AMF and B. japonicum improved catalase (CAT) and peroxidase (POD) in the seeds, and a reverse trend was observed in case of malonaldehyde (MDA) and proline under drought stress. The relative expression of the CAT and POD genes was up-regulated by the application of biofertilizers treatments under drought stress condition. Interestingly a reverse trend was observed in the case of the relative expression of the genes involved in the proline metabolism such as P5CS, P5CR, PDH, and P5CDH under the same conditions. The present study suggests that biofertilizers diminished the inhibitory effect of drought stress on cell development and resulted in a shorter time for DNA accumulation and the cycle of cell division. There were notable changes in the activities of enzymes involved in the secondary metabolism and expression levels of GmSPS1, GmSuSy, and GmC-INV in the plants treated with biofertilizers and exposed to the drought stress at both R3 and R5 stages. These changes in the activities of secondary metabolism and their transcriptional levels caused by biofertilizers may contribute to increasing soybean tolerance to drought stress. Conclusions The results of this study suggest that application of biofertilizers to soybean plants is a promising approach to alleviate drought stress effects on growth performance of soybean plants. The integrated application of biofertilizers may help to obtain improved resilience of the agro ecosystems to adverse impacts of climate change and help to improve soil fertility and plant growth under drought stress.

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A Meta-Analytical Approach on Arbuscular Mycorrhizal Fungi Inoculation Efficiency on Plant Growth and Nutrient Uptake

Agriculture ◽

10.3390/agriculture10090370 ◽

2020 ◽

Vol 10 (9) ◽

pp. 370

Author(s):

Murugesan Chandrasekaran

Keyword(s):

Plant Growth ◽

Arbuscular Mycorrhizal Fungi ◽

Nutrient Uptake ◽

Mycorrhizal Fungi ◽

Host Plants ◽

Plant Biomass ◽

Meta Analysis ◽

Arbuscular Mycorrhizal ◽

Growth Responses ◽

Mycorrhizal Plants

Arbuscular mycorrhizal fungi (AMF) are obligate symbionts of higher plants which increase the growth and nutrient uptake of host plants. The primary objective was initiated based on analyzing the enormity of optimal effects upon AMF inoculation in a comparative bias between mycorrhizal and non-mycorrhizal plants stipulated on plant biomass and nutrient uptake. Consequently, in accomplishing the above-mentioned objective a vast literature was collected, analyzed, and evaluated to establish a weighted meta-analysis irrespective of AMF species, plant species, family and functional group, and experimental conditions in the context of beneficial effects of AMF. I found a significant increase in the shoot, root, and total biomass by 36.3%, 28.5%, and, 29.7%, respectively. Moreover, mycorrhizal plants significantly increased phosphorus, nitrogen, and potassium uptake by 36.3%, 22.1%, and 18.5%, respectively. Affirmatively upon cross-verification studies, plant growth parameters intensification was accredited to AMF (Rhizophagus fasciculatus followed by Funniliforme mosseae), plants (Triticum aestivum followed by Solanum lycopersicum), and plant functional groups (dicot, herbs, and perennial) were the additional vital important significant predictor variables of plant growth responses. Therefore, the meta-analysis concluded that the emancipated prominent root characteristics, increased morphological traits that eventually help the host plants for efficient phosphorus uptake, thereby enhancing plant biomass. The present analysis can be rationalized for any plant stress and assessment of any microbial agent that contributes to plant growth promotion.

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