Soil bacteriostasis limitation in growth of soil and rhizosphere bacteria

1973 ◽  
Vol 19 (2) ◽  
pp. 195-199 ◽  
Author(s):  
Margaret E. Brown
Keyword(s):  
Root Exudates ◽  
Soil Bacteria ◽  
Wheat Root ◽  
Rhizosphere Bacteria ◽  
Mineral Salts ◽  
Air Drying ◽  
Soil Extracts ◽  
Wheat Rhizosphere ◽  
Acid Ph ◽  
Disk Method

Sensitivity of soil bacteria to bacteriostasis was assessed by an agar disk method. Most bacteria isolated from wheat rhizosphere (98%) were sensitive and those not stimulated by roots were not sensitive. Bacteriostasis was always overcome by the addition of wheat root exudates to the disks and sometimes by the addition of glucose or mineral salts. Bacteriostasis was active in all six soils studied but less so in those with acid pH. Bacteriostasis was removed partially by air-drying the soil and totally by sterilizing. Filtrates of soil extracts retained some activity unless completely sterile.

Nitrogen fixation and crop productivity enhancements codriven by intercrop root exudates and key rhizosphere bacteria

2021 ◽  
Author(s):  
Heng‐Yu Hu ◽  
Hong Li ◽  
Min‐Min Hao ◽  
Ya‐Nan Ren ◽  
Meng‐Kun Zhang ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Root Exudates ◽  
Crop Productivity ◽  
Rhizosphere Bacteria

scholarly journals Bio-herbicidal potential of wheat rhizosphere bacteria on Avena fatua L. grass

Bioengineered ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 516-526
Author(s):  
Wei Li ◽  
Shuo Shen ◽  
Hongyu Chen
Keyword(s):  
Avena Fatua ◽  
Rhizosphere Bacteria ◽  
Wheat Rhizosphere

Influence of Temperature and Plant Growth Stages of Red Clover and Wheat on Small Broomrape (Orobanche minor) Germination

2014 ◽  
Vol 28 (1) ◽  
pp. 266-271 ◽  
Author(s):  
Salam A. Al-Thahabi ◽  
Jed B. Colquhoun ◽  
Carol A. Mallory-Smith
Keyword(s):  
Seed Germination ◽  
Root Exudates ◽  
Integrated Management ◽  
Red Clover ◽  
Wheat Root ◽  
Management Plan ◽  
Growth Stages ◽  
Plant Growth Stages ◽  
Different Temperatures ◽  
Infested Field

Small broomrape is a holoparasitic plant that attaches to the roots of red clover as well as several other host plants. Hosts and false hosts produce stimulants that induce small broomrape germination but small broomrape does not attach to a false host. Wheat has been identified as a false host for small broomrape; therefore, studies were conducted to investigate the effect of red clover and wheat root exudates on small broomrape germination. In one study, the effect of exudates from red clover and wheat at multiple growth stages on small broomrape germination was evaluated. Red clover induced small broomrape germination at all growth stages tested but was greatest (78%) in the presence of exudates from red clover at the three-trifoliolate stage. Maximum small broomrape germination was 25% when exposed to exudates produced by one-leaf-stage wheat. In a second study, the relationship between small broomrape germination and host growth condition was evaluated using root exudates from red clover or wheat grown under several temperature conditions for either 4 or 8 wk. For the different temperatures, there were no differences in small broomrape germination when exudates of red clover grown for 4 wk were used. Small broomrape germination was reduced when exposed to exudates from red clover plants grown for 8 wk at 10 C compared with plants grown at 15, 20, and 25 C. Differences in small broomrape seed germination were observed with temperature under which wheat was grown for 4 wk, but not for 8 wk. Although wheat exudates resulted in less small broomrape seed germination than red clover exudates, growing wheat as a false host in a small broomrape-infested field could be an important component of an integrated management plan.

scholarly journals Investigating the role of root exudates in recruiting Streptomyces bacteria to the Arabidopsis thaliana root microbiome

2020 ◽  
Author(s):  
Sarah F. Worsley ◽  
Michael Macey ◽  
Sam Prudence ◽  
Barrie Wilkinson ◽  
J. Colin Murrell ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Stable Isotope ◽  
Plant Growth ◽  
Root Exudates ◽  
Soil Bacteria ◽  
Stable Isotope Probing ◽  
Plant Roots ◽  
Plant Metabolites ◽  
Complex Organic ◽  
Root Microbiome

AbstractStreptomyces species are saprophytic soil bacteria that produce a diverse array of specialised metabolites, including half of all known antibiotics. They are also rhizobacteria and plant endophytes that can promote plant growth and protect against disease. Several studies have shown that streptomycetes are enriched in the rhizosphere and endosphere of the model plant Arabidopsis thaliana. Here, we set out to test the hypothesis that they are attracted to plant roots by root exudates, and specifically by the plant phytohormone salicylate, which they might use as a nutrient source. We confirmed a previously published report that salicylate over-producing cpr5 plants are colonised more readily by streptomycetes but found that salicylate-deficient sid2-2 and pad4 plants had the same levels of root colonisation by Streptomyces bacteria as the wild-type plants. We then tested eight genome sequenced Streptomyces endophyte strains in vitro and found that none were attracted to or could grow on salicylate as a sole carbon source. We next used 13CO2 DNA stable isotope probing to test whether Streptomyces species can feed off a wider range of plant metabolites but found that Streptomyces bacteria were outcompeted by faster growing proteobacteria and did not incorporate photosynthetically fixed carbon into their DNA. We conclude that, given their saprotrophic nature and under conditions of high competition, streptomycetes most likely feed on more complex organic material shed by growing plant roots. Understanding the factors that impact the competitiveness of strains in the plant root microbiome could have consequences for the effective application of biocontrol strains.ImportanceStreptomyces bacteria are ubiquitous in soil but their role as rhizobacteria is less well studied. Our recent work demonstrated that streptomycetes isolated from A. thaliana roots can promote growth and protect against disease across plant species and that plant growth hormones can modulate the production of bioactive specialised metabolites by these strains. Here we used 13CO2 DNA stable isotope probing to identify which bacteria feed on plant metabolites in the A. thaliana rhizosphere and, for the first time, in the endosphere. We found that Streptomyces species are outcompeted for these metabolites by faster growing proteobacteria and instead likely subsist on more complex organic material such as cellulose derived from plant cell material that is shed from the roots. This work thus reveals the “winners and losers” in the battle between soil bacteria for plant metabolites and could inform the development of methods to apply streptomycetes as plant growth-promoting agents.

THE APPLICATION OF A NUTRITIONAL GROUPING METHOD TO SOIL FUNGI

1955 ◽  
Vol 33 (3) ◽  
pp. 281-288 ◽  
Author(s):  
R. G. Atkinson ◽  
J. B. Robinson
Keyword(s):  
Amino Acids ◽  
Growth Factors ◽  
Yeast Extract ◽  
Soil Fungi ◽  
Basal Medium ◽  
Maximum Growth ◽  
Potassium Nitrate ◽  
Soil Extract ◽  
Mineral Salts ◽  
Soil Extracts

In tests with seven different liquid media in which the common nitrogen source was potassium nitrate and the carbohydrate substrate was glucose, at a concentration of only 0.1%, most of the 1914 soil fungi isolated fell into one of three nutritional groups requiring, respectively, for maximum growth amino acids, amino acids plus growth factors, or yeast extract. Relatively few isolates required growth factors alone or a combination of yeast and soil extracts. Most of the isolates grew poorly in the basal medium containing only mineral salts, and glucose, with or without soil extract. Although fungi requiring yeast extract were much less frequently isolated from soil on, rather than remote from, tubers grown in a soybean green-manured plot, isolates requiring amino acids, or yeast plus soil extracts, were correspondingly increased on immature and mature tubers, respectively. In a second plot, however, not specially treated, no differences were observed in the nutritional spectra of fungi isolated from the two kinds of soil environment.

scholarly journals Dihydroxyacetone of wheat root exudates serves as an attractant for Heterodera avenae

PLoS ONE ◽  
2020 ◽  
Vol 15 (7) ◽  
pp. e0236317
Author(s):  
Gaofeng Wang ◽  
Yunhe Wang ◽  
Hazem Abdelnabby ◽  
Xueqiong Xiao ◽  
Wenkun Huang ◽  
...  
Keyword(s):  
Root Exudates ◽  
Wheat Root ◽  
Heterodera Avenae
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