Receptor modifiers indicate that 4-aminobutyric acid (GABA) is a potential modulator of ion transport in plants

GABA (4-aminobutyric acid) is a ubiquitousnon-protein amino acid that accumulates rapidly inplants in response to stress. GABA was firstidentified in plants (potato tubers) and animals(brain tissue) 50 years ago. Although GABA is nowrecognized as the most important inhibitoryneurotransmitter in the mammalian central nervoussystem (CNS), the role of GABA in plants remainsunclear. Studies were performed using Lemna toinvestigate the possibility that GABA elicits aresponse in plants that may be related to that of asignaling molecule as described for GABA effects onthe CNS. Lemna growth was increased 2 to 3-foldby 5 mM GABA, but growth was strongly inhibited by 0.5mM of the isomers 3-aminobutyric acid and2-aminobutyric acid. Growth promotion by GABA wasrapidly terminated by addition of 2-aminobutyric acidto the culture medium, but inhibitory effects of2-aminobutyric acid were not reversed by GABAregardless of amounts added. Promotion of Lemnagrowth by GABA was associated with an increase inmineral content of treated plants in a dose dependentmanner. Results support the hypothesis that GABAactivity in plants involves an effect on ion transportand an interaction with a receptor. Evidence for GABAreceptors in Lemna was obtained from experimentswith pharmacological agents that have been used toidentify GABA receptors in animals. GABA mediatedpromotion of Lemna growth was inhibited bybicuculline and picrotoxin, which are respectivelycompetitive and non-competitive antagonists of GABAreceptors in the CNS. Growth inhibition bybicuculline was not relieved by increasing the amountsof GABA in the medium, indicating that the alkaloid isnot acting, as in the CNS, by competitive antagonismof GABA at GABA receptor sites. Baclofen, a GABAagonist that promotes GABA activity in animalssignificantly increased GABA mediated promotion ofLemna growth. These findings and the knownaction of GABA in regulating ion channels in animalssuggests a way that GABA could amplify the stressresponse in plants.     

The Effect of Bacillus subtilis on in vitro Growth and Pathogenicity of Agrobacterium tumefaciens

Five isolates of Bacillus subtilis isolated from the soil, were found to be antagonistic to 6 isolates of Agrobacterium tumefaciens in vitro. Inoculation of B. subtilis in wounded castor bean plants 30 min before or simultaneous inoculation with A. tumefaciens resulted in excellent control of the crown gall symptoms on the host within 50 days of inoculation. Application of B. subtilis 30 min after inoculation with A. tumefaciens did not result in appreciable disease reduction. Treatment of the tested plants by B. subtilis did not induce any phytotoxic injury or growth retarding side effects. It appears that B. subtilis could potentially be incorporated for crown gall control. However, further tests are needed to test this biological control agent with other plant species especially fruits, nuts and vine nursery stock.     

Biocontrol Efficacy of Bacillus subtilis Strains Isolated from Cow Dung Against Postharvest Yam (Dioscorea rotundata L.) Pathogens

The biocontrol potential of Bacillus subtilis isolated from cow dung microflora was investigated in vitro and in vivo against two postharvest yam pathogenic fungi, Fusarium oxysporum and Botryodiplodia theobromae. B. subtilis strains inhibited the growth of F. oxysporum and B. theobromae in vitro in liquid medium in the range of 49.3–56.6% and in solid medium in the range of 31.0–36.0%, in comparison to the corresponding growth of fungi without bacterial inoculation. The interaction between B. subtilis CM1 and F. oxysporum was also studied by scanning electron microscopy. Chitinase production was demonstrated in vitro when B. subtilis was grown in the presence of colloidal chitin as the sole carbon source in a liquid medium. In vivo study showed that B. subtilis strains inhibited the growth of fungi (F. oxysporum and B. thobromae) up to 83% in wound cavities of yam tubers.     

Plant defense approach of Bacillus subtilis (BERA 71) against Macrophomina phaseolina (Tassi) Goid in mung bean

This study was aimed to elucidate the mitigation mechanism of an endophytic bacterium, Bacillus subtilis (BERA 71) against Macrophomina phaseolina (Tassi) Goid disease in mung bean. M. phaseolina reduced the plant growth by inducing disease, hydrogen peroxide (H₂O₂) and lipid peroxidation. The inoculation of B. subtilis to diseased plants increased chlorophyll, ascorbic acids, and superoxide dismutase, catalase, peroxidase, ascorbate peroxidase and glutathione reductase activities, and while inhibited H₂O₂ and lipid peroxidation for enhancing plant growth. In addition, B. subtilis association in plants mitigated the M. phaseolina infection due to increase of indole acetic acids and indole butyric acid, and also a decrease of abscisic acid. However, the nutrients (N, K, Ca, Mg, Zn, Cu, Mn and Fe) were increased, except Na in M. phaseolina diseased plants treated with B. subtilis. The result of this study suggests that B. subtilis interaction with plants can modulate the metabolism of pigments, hormones, antioxidants and nutrients against M. phaseolina to induce disease resistance in mung bean.     

Metabolism of Sulfur Compounds in Bacillus subtilis during Sporulation

Metabolism of various sulfur compounds in Bacillus subtilis during growth and sporulation was investigated by use of tracer techniques, in an attempt to clarify the mechanism involved in the formation of cystine rich protein of the spore coat.

Methionine, homocysteine, cystathionine, cysteine and some inorganic sulfur compounds (sulfate, sulfite and thiosulfate) were utilized by this organism as sulfur sources for its growth and sporulation. Biosynthesis of methionine from sulfate during growth was more or less inhibited by the addition of cysteine, homocysteine or cystathionine to the culture.

It is suggested from these results that in Bacillus subtilis methionine is synthesized from sulfate through cysteine, cystathionine and homocysteine as is the case in Salmonella or Neurospora. The results also suggest that the metabolism of sulfur-containing amino acids in Bacillus subtilis is strongly regulated by methionine and homocysteine.     

Screening of marine actinobacteria for amylase enzymes inhibitors

Amylase inhibitor producing actinobacteria were isolated and characterized from terrestrial environment and there is no much report found from marine environment, hence in the present study, 17 strains isolated from the rhizosphere sediments of mangroves were tested for their amylase inhibition ability. Seawater requirement test for the growth of actinobacteria found that the strains SSR-3, SSR-12 and SSR-16 requires at least 50% and SSR-6 requires at least 25% seawater for their growth. The inhibition activity of both prokaryotic and eukaryotic amylase was tested by using Bacillus subtilis and Aspergillus niger. The maximum amylase activity (40mm) produced by the A. niger was taken as positive control, when the test actinobacteria strains grown in the medium they inhibited amylase activity and was evidenced by the reduction in inhibition zone (14–37 mm) similarly the amylase produced by the Bacillus subtilis was also recorded maximum (35 mm) amylase activity and was taken as positive control, and the test atinobacterial strains reduced enzyme action(12–33 mm) it varied levals. This indicates that the actinobacteria strains were controlled amylase enzyme activity in both the cases. The strain SSR-10 was highly effective and SSR-8 was less effective in inhibiting eukaryotic amylase produced by A. niger. The strain SSR-2 was effective and SSR-6 showed very less effect in inhibiting the prokaryotic amylase produced by the B subtilis.     

Expression and secretion of a single-chain sweet protein monellin in <Emphasis Type="Italic">Bacillus subtilis</Emphasis> by <Emphasis Type="Italic">sacB</Emphasis> promoter and signal peptide

The sweet protein monellin gene was expressed in Bacillus subtilis under the control of the Bacillus subtilis sacB promoter and signal peptide sequence. A 294-bp DNA fragment, coding for sweet protein monellin, was ligated into the Escherichia coli/B. subtilis shuttle vector pHPC, producing pHPMS, which was subsequently transformed into B. subtilis QB1098, DB104, and DB403. The peptide efficiently directed the secretion of monellin from the recombinant B. subtilis cells. A maximum yield of monellin of 0.29 g protein l⁻¹ was obtained from the supernatant of B. subtilis DB403 harboring pHPMS. SDS-PAGE confirmed the purity of the recombinant product.     

Expression of a Clostridium thermocellum xylanase gene in Bacillus subtilis

Summary The native promoter of a xylanase gene isolated from Clostridium thermocellum was replaced with a strong promoter screened from Bacillus subtilis chromosomes. A part of the C-terminal region of the gene which is not related to the xylanase activity was removed. With the modified xylanase gene, B. subtilis was transformed and grown in LB medium. The xylanase gene was expressed well in B. subtilis and extracellular xylanase was produced up to 30 units per ml when the growth reached OD₆₀₀ of 4.8.     

Suppression of sugar beet damping-off caused by Rhizoctonia solani using bacterial and fungal antagonists

Rhizoctonia damping-off caused by Rhizoctonia solani Kühn, is one of the most damaging sugar beet diseases. It causes serious economic damage wherever sugar beets are grown. Biological control is an efficient and environmentally friendly way to prevent damping-off disease. Suppression of damping-off disease caused by R. solani was carried out by four isolates of Bacillus subtilis (Ehrenberg) Cohn as well as three isolates of each of Trichoderma harzianum Rifai and Trichoderma hamatum (Bonord.) Bainier. The effect of Bacillus and Trichoderma isolates against R. solani was investigated in vitro and tested on sugar beet plants under greenhouse conditions. Isolates of Bacillus and Trichoderma were able to inhibit the growth of R. solani in dual culture. Furthermore, Trichoderma isolates gave high antagonistic effect than isolates of B. subtilis. Under greenhouse conditions, coating seeds by T. harzianum and B. subtilis separately, reduced seedling damping-off significantly. However, applications of T. harzianum increased the percentage of surviving plants more than B. subtilis in comparison to control. The obtained results indicate that T. harzianum and B. subtilis are very effective biocontrol agents that offer potential benefit in sugar beet damping-off and should be harnessed for further biocontrol applications.     

Rhizobacterial-mediated induction of defense enzymes to enhance the resistance of turmeric (Curcuma longa L) to Pythium aphanidermatum causing rhizome rot

Rhizobacteria isolated from the rhizosphere soil were evaluated for their ability to control rhizome rot in turmeric (Curcuma longa L). These isolates were characterised as Pseudomonas fluorescens and Bacillus subtilis. Under in vitro condition, two isolates, namely P. chlororaphis (PcPA23) and B. subtilis (BsCBE4), showed maximum inhibition of mycelial growth of Pythium aphanidermatum, were found effective in reducing rhizome rot of turmeric both under greenhouse and field conditions and increased the plant growth and rhizome yield. Both the isolates were further tested for its ability to induce production of defense-related enzymes and chemicals in plants. Increased activities of phenylalanine ammonia lyase, peroxidase, polyphenol oxidase, chitinase and β-1,3-glucanase were observed in PcPA23 and BsCBE4 pre-treated turmeric plants challenged with P. aphanidermatum. Moreover, higher accumulation of phenolics was noticed in plants pre-treated with PcPA23 and BsCBE4 challenged with P. aphanidermatum. Thus, the present study shows that in addition to direct antagonism and plant growth promotion, induction of defense-related enzymes involved in the phenyl propanoid pathway collectively contributed to enhance resistance against invasion of Pythium in turmeric.     

Inhibitory effects of soluble MD‐2 and soluble CD14 on bacterial growth

The effects of the soluble forms of the endotoxin receptor molecules sMD‐2 and sCD14 on bacterial growth were studied. When Escherichia coli and Bacillus subtilis were incubated at 37°C for 18 hr with either sMD‐2 or sCD14, growth of these bacteria was significantly inhibited as evaluated by viable cell counts and NADPH/NADH activity. A mutant of sCD14 (sCD14d57‐64) lacking a region essential for LPS binding did not inhibit the growth of E. coli, whereas this mutant did inhibit the growth of B. subtilis. Addition of excess PG to the bacterial culture reversed the inhibitory effect of sMD‐2 on the growth of B. subtilis, but not on the growth of E. coli. Furthermore, when evaluated by ELISA, both sMD‐2 and sCD14 bound specifically to PG. Taken together, these results indicate that sMD‐2 and sCD14 inhibit the growth of both Gram‐positive and Gram‐negative bacteria and further suggest that binding to PG and LPS is involved in the inhibitory effect of sMD‐2 on Gram‐positive bacteria and of sCD14 on Gram‐negative bacteria, respectively.     

Role of Ni-tolerant Bacillus spp. and Althea rosea L. in the phytoremediation of Ni-contaminated soils

In our current study, four nickel-tolerant (Ni-tolerant) bacterial species viz, Bacillus thuringiensis 002, Bacillus fortis 162, Bacillus subtilis 174, and Bacillus farraginis 354, were screened using Ni-contaminated media. The screened microbes exhibited positive results for synthesis of indole acetic acid (IAA), siderophore production, and phosphate solubilization. The effects of these screened microbes on Ni mobility in the soil, root elongation, plant biomass, and Ni uptake in Althea rosea plants grown in Ni-contaminated soil (200 mg Ni kg^?1) were evaluated. Significantly higher value for water-extractable Ni (38 mg kg^?1) was observed in case of Ni-amended soils inoculated with B. subtilis 174. Similarly, B. thuringiensis 002, B. fortis 162, and B. subtilis 174 significantly enhanced growth and Ni uptake in A. rosea. The Ni uptake in the shoots and roots of B. subtilis 174-inoculated plants enhanced up to 1.7 and 1.6-fold, respectively, as compared to that in the un-inoculated control. Bacterial inoculation also significantly improved the root and shoot biomass of treated plants. The current study presents a novel approach for bacteria-assisted phytoremediation of Ni-contaminated areas.     

Effect of berberine on growth of the callus cultures of several species

A bacteriostatic concentration of berberine much inhibited growth of the callus cultures ofLithospermum erythrorhizon, Datura inooxia andCarthamus tinctorius, but little inhibited the callus growth ofMacleaya cordata. On the other hand, the high concentration of berberine tended to stimulate the callus growth ofCoptis japonica var.japonica. Among callus cultures of the five species described above, 4-desoxypyridoxine inhibited growth of the callus cultures ofD. innoxia andC. tinctorius. In these two callus cultures, recovery effects of some of the vitamin B₆ group (10 μg/ml) on the inhibition of callus growth by berberine (100 μg/ml) or 4-desoxypyridoxine (50 μg/ml) were observed.     

Growth and chlorophyll production in plant callus tissues grown in vitro

Summary Growth, nutrition and chlorophyll development were studied in chlorophyllous callus tissues isolated from the following edible angiospermous plants: carrot root, crown gall of tomato, endive embryo, leaf petiole and stem of lettuce, leaf petiole of parsley, pea stem and rose stem. Growth patterns of these tissues in vitro were sigmoid. Synthetic media produced less growth, in terms of fresh weight increase, than media containing coconut milk, a highly complex and little understood natural substance. Murashige and Skoog's synthetic medium proved useful for satisfactory growth and chlorophyll production in a number of tissues. Its usefulness was further increased by additional amounts of copper sulphate, potassium nitrate and monobasic ammonium phosphate. Increased levels of iron and magnesium inhibited growth. Incorporation of yeast extract in the tobacco-high-salts-medium produced the highest amount of growth and chlorophyll formation in endive tissue. Presence of exogenous sucrose was essential for the continued good growth of the above callus tissues in vitro. Highest amount of growth took place either in white light or in the dark. Different tissues had different responses to high or low intensities of light. Endive and carrot tissues produced in vitro were palatable to human taste. Endive tissue was particularly good as it also differentiated many small rosettes of leaves, shoots and had a mild aromatic flavor typical of the endive plants grown in nature.     

Ansamycin Antibiotics as Free Radical Scavengers Isolated from Streptomyces by Using the Bactericidal Action of the Hydroxyl Radical

Ansamycin antibiotics (1–4) were isolated from the cultured broth of Streptomyces sp. USF-319 strain as a result of our screening for free radical scavengers. They inhibited the bactericidal effect of the Fenton reagent toward Bacillus subtilis by their radical scavenging activity. Some of them also showed inhibitory activity against lipid peroxidation and lipoxygenases.     

Strong growth limitation of a floating plant (Lemna gibba) by the submerged macrophyte (Elodea nuttallii) under laboratory conditions

1. The asymmetric competition for light and nutrients between floating and submerged aquatic plants is thought to be key in explaining why dominance by either of these groups can be stable and difficult to change. 2. Although the shading effect of floating plants on submerged plants has been well documented, the impact of submerged plants on floating plants has been poorly explored hitherto. 3. Here, we used laboratory experiments to examine how submerged plant (Elodea nuttallii) alter nutrient conditions in the water column and how this affects the growth of floating plants (Lemna gibba). 4. We demonstrate that, at higher nutrient concentrations, Lemna is increasingly likely to outcompete Elodea. 5. Under low nutrient concentrations (0.1–2 mg N L^?1) Elodea can strongly reduce the growth of Lemna. Growth of floating plants virtually stopped in some of the experiments with Elodea. 6. Extremely reduced tissue N, Mn, chlorophyll and elongated roots indicated that the growth inhibition of Lemna by Elodea was predominantly caused by the latter’s impact on the nutrient conditions for floating plants. 7. These results strengthen the hypothesis that submerged plants can prevent colonization of a lake by floating plants.     

椿根皮的化学成分及抑菌活性研究

为探寻椿根皮抑菌的物质基础，该研究采用硅胶、Sephadex LH-20等方法对椿根皮甲醇提取物进行分离和纯化，通过理化性质和波谱数据分析单体化合物的结构，并以卡那霉素为对照组采用流式细胞法测试化合物的抑菌活性。结果表明：从椿根皮中得到22个化合物，分别鉴定为pleuchiol (1)、withastramonolide (2)、7-ketositosterol (3)、白桦酯醇(4)、桦木酸甲酯(5)、1, 2, 4-trimethoxybenzene (6)、顺丁烯二酸二甲酯(7)、sonderianol (8)、dibutyl phthalate (9)、pinoresinol (10)、对羟基苯甲酸乙酯(11)、avenalumic acid methyl ester (12)、5,3′-dihydroxy-3,7,4′-trimethoxy-flavone (13)、spathulenol (14)、2-甲基-5-丙基酮-7-羟基色原酮(15)、 7,4′-dihydroxyflavone (16)、annphenone (17)、3-羟基-4-甲氧基苯甲酸(18)、5,3′...     

Enhanced Hydrocarbons Degradation in the Rhizosphere of Mangrove Plants by a Halophilic Bacillus Subtilis Subtilis Strain

Sulaibikhat Embayment is a severely contaminated coastline in the State of Kuwait. The contaminating pollutants include hydrocarbons, heavy metals, and suspended particles. The objective of this study is to assess the ability of mangroves planted in the Sulaibikhat Embayment to enhance hydrocarbons degradation by the activities of rhizospheric hydrocarbon degrading bacteria (HDB). Accordingly, samples were collected from the rhizosphere of selected mangrove plants and from sediments in the same location but away from mangrove marshes. The samples were analyzed chemically and microbiologically before being enriched with a mixture of hydrocarbon compounds (HC) to isolate HDB.

A number of halophilic HDB were isolated from mangroves rhizosphere and the surrounding sediments such as Pseudomonas balearica, Microbacterium barkeri and Gordonia soli. On the other hand, Bacillus velezensis and Bacillus subtilis subtilis were both isolated only from mangroves rhizosphere. Among the isolated HDB, Bacillus subtilis subtilis was distinguished with its high degradation rates of the tested HC including poly aromatic hydrocarbons. According to our knowledge, this is the first Bacillus subtilis HC-degrading strain that was isolated from Kuwait Bay and from mangroves rhizosphere.