Decomposition of peatland DOC affected by root exudates is driven by specific r and K strategic bacterial taxa

AbstractIn peatlands, decomposition of organic matter is limited by harsh environmental conditions and low decomposability of the plant material. Shifting vegetation composition from Sphagnum towards vascular plants is expected in response to climate change, which will lead to increased root exudate flux to the soil and stimulation of microbial growth and activity. We aimed to evaluate the effect of root exudates on the decomposition of recalcitrant dissolved organic carbon (DOC) and to identify microorganisms involved in this process. The exudation was mimicked by an addition of a mixture of 13C labelled compounds into the recalcitrant DOC in two realistic levels; 2% and 5% of total DOC and peatland porewater with added root exudates was incubated under controlled conditions in the lab. The early stage of incubation was characterized by a relative increase of r-strategic bacteria mainly from Gammaproteobacteria and Bacteriodetes phyla within the microbial community and their preferential use of the added compounds. At the later stage, Alphaproteobacteria and Acidobacteria members were the dominating phyla, which metabolized both the transformed 13C compounds and the recalcitrant DOC. Only higher exudate input (5% of total DOC) stimulated decomposition of recalcitrant DOC compared to non-amended control. The most important taxa with a potential to decompose complex DOC compounds were identified as: Mucilaginibacter (Bacteriodetes), Burkholderia and Pseudomonas (Gammaproteobacteria) among r-strategists and Bryocella and Candidatus Solibacter (Acidobacteria) among K-strategists. We conclude that increased root exudate inputs and their increasing C/N ratio stimulate growth and degradation potential of both r-strategic and K-strategic bacteria, which make the system more dynamic and may accelerate decomposition of peatland recalcitrant DOC.

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Root exudate input stimulates peatland recalcitrant DOC decomposition by r-strategic taxa of Gammaproteobacteria and Bacteroidetes

10.21203/rs.2.21088/v1 ◽

2020 ◽

Author(s):

Jiří Mastný ◽

Jiří Bárta ◽

Eva Kaštovská ◽

Tomáš Picek

Keyword(s):

Organic Matter ◽

Community Composition ◽

Plant Community ◽

Root Exudates ◽

Early Stage ◽

Gene Copy Number ◽

Gene Copy ◽

Plant Community Composition ◽

Microbial Decomposition ◽

Decomposition Of Organic Matter

Abstract Background In peatlands, decomposition of organic matter is limited by harsh environmental conditions and low decomposability of the plant material. Increased microbial decomposition of organic matter in peatland ecosystems may become an important phenomenon in the near future after the expected shift in plant community composition from Sphagnum to vascular plants due to climate change. Such a change in plant community composition will lead to increased root exudates flux to the soil and stimulation of microbial growth and activity. The aim of our study was to evaluate the effect of root exudates on the decomposition of recalcitrant dissolved organic carbon (DOC) and identify the microorganisms responsible for this process. Results Decomposition of recalcitrant DOC was stimulated by a high levels of 13 C labelled root exudates addition whereas it was suppressed by a low levels of root exudates addition. Recalcitrant DOC decomposition was positively related to the exudate C/N ratio as a result of enhanced “microbial nutrient mining” due to a deepening of microbial nutrient limitation. The early stage of incubation immediately following the exudate addition was characterized by the preferential use of the added compounds at the expense of recalcitrant DOC. At the same time, r-strategic bacteria (identification based on average 16SrRNA gene copy number) belonging to mainly to Gammaproteobacteria and Bacteriodete s phyla relatively increased within the microbial community. At the later stage, this more abundant bacterial community was replaced by a less abundant community composed of bacteria mostly belonging to Alphaproteobacteria and Acidobacteria . The most important taxa with the potential to decompose complex compounds were indentified: Mucilaginibacter ( Bacteriodete s), Burkholderia and Pseudomonas ( Gammaproteobacteria ) among r-strategists and Bryocella and Candidatus Solibacter ( Acidobacteria ) among K-strategists. Conclusions Increased inputs of root exudates, with a higher C/N ratio, may stimulate decomposition of peatland recalcitrant DOC. In this, bacteria were found to be more important than fungi. Our experiment indicates that r-strategic bacteria as well as K-strategists can be important in stimulated decomposing of recalcitrant peatland DOC.

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IN VITRO DEGRADATION OF MIMOSINE BY MICROORGANISMS FROM THE ESOPHAGEAL SAC OF VOLES (Microtus arvalis)

Canadian Journal of Animal Science ◽

10.4141/cjas86-058 ◽

1986 ◽

Vol 66 (2) ◽

pp. 547-551 ◽

Cited By ~ 2

Author(s):

H. KUDO ◽

K.-J. CHENG ◽

W. MAJAK ◽

J. W. HALL ◽

T. ARAI ◽

...

Keyword(s):

Pyridine Ring ◽

Microbial Growth ◽

Early Stage ◽

Microtus Arvalis ◽

In Vitro Degradation ◽

Ruminal Microorganisms ◽

Highly Active ◽

Alfalfa Hay ◽

Degradation Rates

The microbiota in the esophageal sac of voles fed either cubed alfalfa hay or concentrate pellets were assayed to determine their capacity to anaerobically degrade mimosine in vitro. Differences (P < 0.01) were found between the two diets during the growth phase. The sac contents of voles fed concentrate pellets degraded mimosine and 3-hydroxy-4-(1H)-pyridone (DHP) rapidly, but inocula from voles fed cubed alfalfa hay only hydrolyzed mimosine to DHP. Degradation of the pyridine ring occurred at the early stage of incubation, concurrently with microbial growth. Thereafter, degradation rates appear to have been almost negligible and very similar for both diets. These results agree with previous data obtained with ruminal microorganisms, where highly active inocula were also associated with animals on concentrate diets. Key words: Detoxification, hydrolysis, esophageal sac, mimosine, 3-hydroxy-4- (1H)-pyridone, voles

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Warming increases soil carbon input in a Sibiraea angustata-dominated alpine shrub ecosystem

Journal of Plant Ecology ◽

10.1093/jpe/rtab101 ◽

2021 ◽

Author(s):

Mei Liu ◽

Jia-Hao Wen ◽

Ya-Mei Chen ◽

Wen-Juan Xu ◽

Qiong Wang ◽

...

Keyword(s):

Tibetan Plateau ◽

Root Exudates ◽

Climate Warming ◽

Root Exudate ◽

Soil Organic C ◽

Organic C ◽

Root Litter ◽

C Stocks ◽

Alpine Shrub ◽

Key Drivers

Abstract Aims Plant-derived carbon (C) inputs via foliar litter, root litter and root exudates are key drivers of soil organic C stocks. However, the responses of these three input pathways to climate warming have rarely been studied in alpine shrublands. Methods By employing a three-year warming experiment (increased by1.3 ℃), we investigated the effects of warming on the relative C contributions from foliar litter, root litter and root exudates from Sibiraea angustata, a dominant shrub species in an alpine shrubland on the eastern Qinghai-Tibetan Plateau. Important Findings The soil organic C inputs from foliar litter, root litter and root exudates were 77.45, 90.58 and 26.94 g C m -2, respectively. Warming only slightly increased the soil organic C inputs from foliar litter and root litter by 8.04 and 11.13 g C m -2, but significantly increased the root exudate C input by 15.40 g C m -2. Warming significantly increased the relative C contributions of root exudates to total C inputs by 4.6% but slightly decreased those of foliar litter and root litter by 2.5% and 2.1%, respectively. Our results highlight that climate warming may stimulate plant-derived C inputs into soils mainly through root exudates rather than litter in alpine shrublands on the Qinghai-Tibetan Plateau.

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Identification of Xylem Occlusions Occurring in CutClematis(ClematisL., fam.RanunculaceaeJuss.) Stems during Their Vase Life

The Scientific World JOURNAL ◽

10.1100/2012/749281 ◽

2012 ◽

Vol 2012 ◽

pp. 1-12 ◽

Cited By ~ 7

Author(s):

Agata Jedrzejuk ◽

Julia Rochala ◽

Jacek Zakrzewski ◽

Julita Rabiza-Świder

Keyword(s):

Water Uptake ◽

Plant Material ◽

Microbial Growth ◽

Vascular System ◽

Vase Life ◽

Cut Flower ◽

Cut Flowers ◽

Bacterial Development ◽

Growth Formation ◽

New Treatments

During the vase life of cut stems obstruction of xylem vessels occurs due to microbial growth, formation of tyloses, deposition of materials in the lumen of xylem vessels and the presence of air emboli in the vascular system. Such obstructions may restrict water uptake and its transport towards upwards thus lowering their ornamental value and longevity of cut flowers.Clematisis a very attractive plant material which may be used as cut flower in floral compositions. Nothing is known about the histochemical or cytological nature of xylem blockages occurring in cut stems of this plant. This study shows that inclematis, tyloses are the main source of occlusions, although bacteria and some amorphic substances may also appear inside the vessels. A preservative composed of 200 mg dm−38-HQC (8-hydroxyquinolin citrate) and 2% sucrose arrested bacterial development and the growth of tyloses. This information can be helpful in the development of new treatments to improve keeping qualities of cutclematisstems.

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Virus-Based Immunotherapy of Glioblastoma

Cancers ◽

10.3390/cancers11020186 ◽

2019 ◽

Vol 11 (2) ◽

pp. 186 ◽

Cited By ~ 32

Author(s):

Miika Martikainen ◽

Magnus Essand

Keyword(s):

Immune Responses ◽

Oncolytic Virus ◽

Early Stage ◽

Primary Brain Tumor ◽

Oncolytic Viruses ◽

Preclinical Models ◽

Adjuvant Effect ◽

Cell Responses ◽

Near Future ◽

Stimulation Of

Glioblastoma (GBM) is the most common type of primary brain tumor in adults. Despite recent advances in cancer therapy, including the breakthrough of immunotherapy, the prognosis of GBM patients remains dismal. One of the new promising ways to therapeutically tackle the immunosuppressive GBM microenvironment is the use of engineered viruses that kill tumor cells via direct oncolysis and via stimulation of antitumor immune responses. In this review, we focus on recently published results of phase I/II clinical trials with different oncolytic viruses and the new interesting findings in preclinical models. From syngeneic preclinical GBM models, it seems evident that oncolytic virus-mediated destruction of GBM tissue coupled with strong adjuvant effect, provided by the robust stimulation of innate antiviral immune responses and adaptive anti-tumor T cell responses, can be harnessed as potent immunotherapy against GBM. Although clinical testing of oncolytic viruses against GBM is at an early stage, the promising results from these trials give hope for the effective treatment of GBM in the near future.

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In vitro studies on the behaviour of second-stage juveniles of Heterodera schachtii (Nematoda: Heteroderidae) in response to host plant root exudates

Parasitology ◽

10.1017/s0031182000059394 ◽

1991 ◽

Vol 103 (1) ◽

pp. 149-155 ◽

Cited By ~ 18

Author(s):

F. Grundler ◽

L. Schnibbe ◽

U. Wyss

Keyword(s):

Root Exudates ◽

Root Exudate ◽

Plant Root ◽

Time Lapse ◽

Heterodera Schachtii ◽

Second Stage ◽

Video Recordings ◽

Aseptic Conditions ◽

Agarose Layer

The behaviour of Heterodera schachtii second-stage juveniles in response to mustard (Sinapis alba) rooxudates was observed and analysed under aseptic conditions in a standardized bioassay. Aggregation of juveniles on an agarose layer occurred within less than 30 min in the area where root exudates had been applied and persisted for several hours. Analysis of time-lapse video recordings showed that the aggregation did not result from a directed orientation of the juvenile towards the root exudate. This was supported by an orientation assay using single juveniles. Aggregated juveniles showed pre-infection exploratory behaviour, including stylet thrusting and head-end bending, while staying at rest for several minutes.

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Rootstock-Scion Interaction Affects the Composition and Pathogen Inhibitory Activity of Tobacco (Nicotiana tabacum L.) Root Exudates

Plants ◽

10.3390/plants9121652 ◽

2020 ◽

Vol 9 (12) ◽

pp. 1652

Author(s):

Cheng-Sheng Zhang ◽

Yanfen Zheng ◽

Lijuan Peng ◽

Jianmin Cao

Keyword(s):

Nicotiana Tabacum ◽

Root Exudates ◽

Root Exudate ◽

Phytophthora Nicotianae ◽

Susceptible Cultivar ◽

Black Shank ◽

Nicotiana Tabacum L ◽

Disease Induction ◽

Resistant Rootstock ◽

Ethylhexyl Phthalate

The composition and allelopathy to Phytophthora nicotianae (the causal agent of tobacco black shank disease) of root exudates from a resistant tobacco (Nicotiana tabacum L.) cultivar Gexin 3, a susceptible cultivar Xiaohuangjin 1025 and their reciprocal grafts were investigated. Grafting with disease-resistant rootstock could improve resistance to black shank; this is closely related to the allelopathy of root exudates. The root exudates from the resistant cultivar inhibited the growth of P. nicotianae, while those from the susceptible cultivar promoted the growth; the grafting varieties had intermediate properties. The root exudate composition differed among cultivars. Gexin 3 was rich in esters and fatty acids, while Xiaohuangjin 1025 contained more hydrocarbons and phenolic acids. The composition of root exudates of grafted cultivars as well as their allelopathy to P. nicotianae were altered, and tended to be close to the composition of cultivar used as rootstock. Eugenol, 4-tert-butylphenol, mono (2-ethylhexyl) phthalate, 4-hydroxybenzoic acid, 2,6-di-tert-butylphenol, dipropyl phthalate, and methyl myristate were identified as the main compounds contributing to inhibitory properties of root exudates. Sorbitol was suggested to play a role in disease induction. Overall, rootstock–scion interaction affected the composition of tobacco root exudates, which may be attributed to the different disease resistance among grafted plants, rootstock and scion.

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Effects of the Endophytic Bacteria Bacillus cereus BCM2 on Tomato Root Exudates and Meloidogyne incognita Infection

Plant Disease ◽

10.1094/pdis-11-18-2016-re ◽

2019 ◽

Vol 103 (7) ◽

pp. 1551-1558 ◽

Cited By ~ 4

Author(s):

Xia Li ◽

Hai-Jing Hu ◽

Jing-Yu Li ◽

Cong Wang ◽

Shuang-Lin Chen ◽

...

Keyword(s):

Bacillus Cereus ◽

Root Exudates ◽

Meloidogyne Incognita ◽

Endophytic Bacteria ◽

Root Exudate ◽

Tomato Root ◽

Second Stage ◽

Tomato Roots ◽

Meloidogyne Spp ◽

Root Tissues

Root-knot nematodes (Meloidogyne spp.) cause serious crop losses worldwide. The colonization of tomato roots by endophytic bacteria Bacillus cereus BCM2 can greatly reduce Meloidogyne incognita damage, and tomato roots carrying BCM2 were repellent to M. incognita second-stage juveniles (J2). Here, the effects of BCM2 colonization on the composition of tomato root exudates was evaluated and potential mechanisms for BCM2-mediated M. incognita control explored using a linked twin-pot assay and GC-MS. On water agar plates, J2 preferentially avoided filter paper treated with tomato root exudates (organic phase only) from plants inoculated with BCM2, visiting these 67.1% less than controls. In a linked twin-pot assay, BCM2 treatment resulted in a 42.0% reduction in the number of nematodes in the soil, a 43.3% reduction in the number of galls and a 47.7% decrease in the density of M. incognita in root tissues. Analysis of root exudate composition revealed that BCM2 inoculation increased the number of components in exudates. Among these, 2,4-di-tert-butylphenol, 3,3-dimethyloctane, and n-tridecane secretions markedly increased. In repellency trials on water agar plates, J2 avoided 2,4-di-tert-butylphenol, n-tridecane, and 3,3-dimethyloctane at concentrations of 4 mmol/liter. In a linked twin-pot assay, inoculation with 2,4-di-tert-butylphenol or 3,3-dimethyloctane reduced the number of nematodes in the soil (by 54.9 and 70.6%, respectively), the number of galls (by 53.7 and 52.4%), and the number of M. incognita in root tissues (by 67.5 and 36.3%). BCM2 colonization in tomato roots affected the composition of root exudates, increasing the secretion of substances that appear to be repellent, thus decreasing M. incognita J2 infection of roots.

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Plants colonized by AM fungi regulate further root colonization by AM fungi through altered root exudation

Canadian Journal of Botany ◽

10.1139/b99-052 ◽

1999 ◽

Vol 77 (6) ◽

pp. 891-897 ◽

Cited By ~ 15

Author(s):

Alexandra Pinior ◽

Urs Wyss ◽

Yves Piché ◽

Horst Vierheilig

Keyword(s):

Root Exudates ◽

Glomus Mosseae ◽

Glomus Intraradices ◽

Root Colonization ◽

Root Exudation ◽

Axenic Culture ◽

Am Fungi ◽

Hyphal Growth ◽

Gigaspora Rosea ◽

Stimulation Of

The effect of root exudates from non-mycorrhizal and mycorrhizal cucumber (Cucumis sativus L.) plants colonized by one of three arbuscular mycorrhizal fungi (Gigaspora rosea Nicolson & Schenck, Glomus intraradices Smith & Schenck, or Glomus mosseae (Nicolson & Gerdemann) Gerd. & Trappe) on hyphal growth of Gi. rosea and G. intraradices in axenic culture and on root colonization by G. mosseae in soil was investigated. Root exudates from non-mycorrhizal cucumber plants clearly stimulated hyphal growth, whereas root exudates from all mycorrhizal cucumber plants tested showed no stimulation of the hyphal growth of Gi. rosea and only a slight stimulation of the hyphal growth of G. intraradices. Moreover, root exudates from all mycorrhizal cucumber plants inhibited root colonization by G. mosseae compared with the water-treated controls. These results suggest that plants colonized by AM fungi regulate further mycorrhization via their root exudates.Key words: Glomales, Gigaspora rosea, Glomus intraradices, Glomus mosseae, root exudates, regulation.

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ELECTRICAL STIMULATION OF THE HYPOTHALAMUS AND LUTEINIZING HORMONE SECRETION IN JAPANESE QUAIL

Journal of Endocrinology ◽

10.1677/joe.0.0670431 ◽

1975 ◽

Vol 67 (3) ◽

pp. 431-438 ◽

Cited By ~ 22

Author(s):

D. T. DAVIES ◽

B. K. FOLLETT

Keyword(s):

Electrical Stimulation ◽

Hormone Secretion ◽

Relative Increase ◽

Significant Rise ◽

Bipolar Electrode ◽

Luteinizing Hormone Secretion ◽

Coturnix Coturnix ◽

Electrolytic Lesions ◽

Lh Secretion ◽

Stimulation Of

SUMMARY Experiments were undertaken to localize those hypothalamic areas in the male quail (Coturnix coturnix japonica) where electrical stimulation would increase LH secretion. The posterior basal hypothalamus was stimulated with rectangular pulses (height 500 μA) through a bipolar electrode for 6 min, blood samples being taken for LH assay 20 min before, and 2, 10, 20 and 30 min after stimulation. The highest plasma concentration was observed in the 2 min sample. Over the next 30 min the LH level decreased to the resting concentration. The relative increase in LH level was greatest in sexually immature quail and least in photostimulated castrated birds, although the highest absolute levels were seen in the castrated quail. There were no statistical differences between the magnitude of the LH increases in sexually immature, mature and castrated quail. Various hypothalamic regions were then stimulated with a smaller current (200 μA) applied for only 2 min. A highly significant rise in LH followed stimulation of either the tuberal hypothalamus (postero-dorsal part of the infundibular nuclear complex, PD-INC), or the preoptic region (POR) while stimulation 0·5–1·5 mm away from these regions did not change LH secretion. Stimulation of the anterior basal hypothalamus, or of the suprachiasmatic area, caused a significant rise in LH concentration although this was less than that seen after stimulation of the POR. Stimulation in the POR or the PD-INC was ineffective if the tuberal hypothalamus had been deafferentated surgically some days previously. The data complement the studies in which destruction of the PD-INC or the POR by electrolytic lesions has been shown to block photoperiodically induced testicular growth and LH secretion.

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