Sclerotinia stem rot,caused by Sclerotinia sclerotiorum,is a destructive soil-borne disease leading to huge yield loss.We previously reported that Klebsiella variicola FH-1 could degrade atrazine herbicides,and the ve...Sclerotinia stem rot,caused by Sclerotinia sclerotiorum,is a destructive soil-borne disease leading to huge yield loss.We previously reported that Klebsiella variicola FH-1 could degrade atrazine herbicides,and the vegetative growth of atrazine-sensitive crops(i.e.,soybean)was significantly increased in the FH-1-treated soil.Interestingly,we found that FH-1 could promote soybean growth and induce resistance to S.sclerotiorum.In our study,strain FH-1 could grow in a nitrogen-free environment,dissolve inorganic phosphorus and potassium,and produce indoleacetic acid and a siderophore.The results of pot experiments showed that K.variicola FH-1 promoted soybean plant development,substantially improving plant height,fresh weight,and root length,and induced resistance against S.sclerotiorum infection in soybean leaves.The area under the disease progression curve(AUDPC)for treatment with strain FH-1 was significantly lower than the control and was reduced by up to 42.2%within 48 h(P<0.001).Moreover,strain FH-1 rcovered the activities of catalase,superoxide dismutase,peroxidase,phenylalanine ammonia lyase,and polyphenol oxidase,which are involved in plant protection,and reduced malondialdehyde accumulation in the leaves.The mechanism of induction of resistance appeared to be primarily resulted from the enhancement of transcript levels of PR10,PR12,AOS,CHS,and PDF1.2 genes.The colonization of FH-1 on soybean root,determined using CLSM and SEM,revealed that FH-1 colonized soybean root surfaces,root hairs,and exodermis to form biofilms.In summary,K.variicola FH-1 exhibited the biological control potential by inducing resistance in soybean against S.sclerotiorum infection,providing new suggestions for green prevention and control.展开更多
Among the diverse soil bacteria, plant growth promoting rhizobacteria (PGPR) mark an important role in enhancing plant growth through a range of beneficial functions. This is mainly achieved by effective rhizosphere c...Among the diverse soil bacteria, plant growth promoting rhizobacteria (PGPR) mark an important role in enhancing plant growth through a range of beneficial functions. This is mainly achieved by effective rhizosphere colonization by PGPR. Biofilm development by PGPR is considered as a survival strategy over the planktonic mode of growth under stress and natural conditions. Since the performance of microbial inoculants under field conditions is not always consistent due to various biotic and abiotic factors affecting survival, colonization and functions. Therefore, the rhizobacteria with efficient colonization ability and exhibiting multiple PGP traits are expected to perform better. We hypothesized that the biofilm forming ability of PGPR on plant root will be an added advantage to rhizosphere colonization. Therefore, we have selected a promising isolate of PGPR through random screening programme from rhizoplane of wheat (Triticum aestivum). The selection was based on biofilm development ability, multifarious PGP activities (production of indole acetic acid, sidero-phore, phosphate solubilization, hydrogen cyanide, ammonia production and biocontrol activity) and tolerance to salinity and heavy metals. The selected isolate was identified by 16 s rRNA partial gene sequencing as Pseudomonas entomophila-FAP1. The strain FAP1 formed strong biofilm in microtitre plate, glass surface as well as on the roots of wheat seedlings. Biofilm forming capacity of the FAP1 was characterized by scanning electron microscopy and confocal laser scanning microscopy. FAP1 exhibited biofilm-related traits such as the production of exopolysaccharides, EPS (1501.33 ± 1.08 μg ml-1), alginate (212.81 ± 1.09 μg ml-1), swarming motility (22 ± 1.36 mm), swimming motility (31 ± 2.12 mm) and cell surface hydrophobicity (63%). Rhizosphere colonization by FAP1 was found 7.5 Log CFU g-1 of soil comparable with rhizoplane colonization (7.2 Log CFU g-1 of root). Therefore, biofilm formation on plant roots by promising PGPR may be included as an additional criterion to select a better rhizosphere colonizer. Further, study with mutant deficient in biofilm should be developed for comparative study to explore the exact contribution of biofilm in root colonization under natural soil-plant system.展开更多
Flagellar biosynthesis and motility are subject to a four-tiered transcriptional regulatory circuit in Pseudomonas,and the master regulator FleQ appears to be the highest-level regulator in this hierarchical regulator...Flagellar biosynthesis and motility are subject to a four-tiered transcriptional regulatory circuit in Pseudomonas,and the master regulator FleQ appears to be the highest-level regulator in this hierarchical regulatory cascade.Pseudomonas stutzeri A1501 is motile by a polar flagellum;however,the motility and regulatory mechanisms involved in this process are unknown.Here,we searched the A1501 genome for flagella and motility genes and found that approximately 50 genes,which were distributed in three non-contiguous chromosomal regions,contribute to the formation,regulation and function of the flagella.The non-polar mutation of fleQ impaired flagellar biosynthesis,motility and root colonization but enhanced biofilm formation.FleQ positively regulates the expression of flagellar class Ⅱ-Ⅳ genes,suggesting a regulatory cascade that is coordinated similar to that of the well-known P.aeruginosa.Based on our results,we propose that flagellar genes in P.stutzeri A1501 are regulated in a cascade regulated by FleQ and that flagellum-driven motility properties may be necessary for competitive rhizosphere colonization.展开更多
The colonization features of periphytic diatoms were studied in coastal waters of the Yellow Sea, northern China from May to June 2010, using glass slides as an artificial substratum. Samples were collected at a time ...The colonization features of periphytic diatoms were studied in coastal waters of the Yellow Sea, northern China from May to June 2010, using glass slides as an artificial substratum. Samples were collected at a time interval of 1, 3, 7, 10, 14, 21 and 28 d from two depths of 1 and 3 m. The dynamics of diatom colonization process had a similar pattern in community structure and fitted the logistic model in growth curve at both depths. The maximum abundance and the time for reaching 50% maximum abundance （10 d） showed no significant differences （P〉0.05） between two depths 1 and 3 m. Although the diatom communities repre- sented similar taxonomic composition, they differed in the temporal pattern of structural parameters and in succession dynamics of dominant species between the two layers. The species richness showed significantly higher values during the colonization period more than 14 d, while the species diversity and evenness rep- resented a higher variability with significantly different values （P〈0.05） at a depth of 1 m than at a deeper layer. The results suggest that the diatom colonization follows the logistic model growth curve and differs in colonization features between different depths in the coastal waters, and that the sampling strategy at i m is more effective to detect the ecological features for bioassessment in marine ecosystems.展开更多
Aim Dental biofilms are complex communities composed largely of harmless bacteria. Certain pathogenic species including Streptococcus mutans （S. mutans） can become predominant when host factors such as dietary sucro...Aim Dental biofilms are complex communities composed largely of harmless bacteria. Certain pathogenic species including Streptococcus mutans （S. mutans） can become predominant when host factors such as dietary sucrose intake imbalance the biofilm ecology. Current approaches to control S. mutans infection are not pathogen-specific and eliminate the entire oral community along with any protective benefits provided. Here, we tested the hypothesis that removal of S. mutans from the oral community through targeted antimicrobial therapy achieves protection against subsequent S. mutans colonization. Methodology Controlled amounts of S. mutans were mixed with S. mutans-free saliva, grown into biofilms and visualized by antibody staining and cfu quantization. Two specifically-targeted antimicrobial peptides （STAMPs） against S. mutans were tested for their ability to reduce S. mutans biofilm incorporation upon treatment of the inocula. The resulting biofilms were also evaluated for their ability to resist subsequent exogenous S. mutans colonization. Results S. mutans colonization was considerably reduced （9 ± 0.4 fold reduction, P=0.01） when the surface was preoccupied with saliva-derived biofilms. Furthermore, treatment with S. mutans-specific STAMPs yielded S. mutans-deficient biofilms with significant protection against further S. mutans colonization （5 minutes treatment： 38 ± 13 fold reduction P=0.01; 16 hours treatment： 96 ± 28 fold reduction P=0.07）. Conclusion S. mutans infection is reduced by the pre- sence of existing biofilms. Thus maintaining a healthy or ＂normal＂ biofilm through targeted antimicrobial therapy （such as the STAMPs） could represent an effective strategy for the treatment and prevention of S. mutans colonization in the oral cavity and caries progression.展开更多
Biofilm-producing bacteria can decrease Cd uptake in vegetables, but mechanisms underlying this effect are poorly characterized. In this study, two mutant strains B12ΔYwcc and B12ΔSlr R were constructed from a biofi...Biofilm-producing bacteria can decrease Cd uptake in vegetables, but mechanisms underlying this effect are poorly characterized. In this study, two mutant strains B12ΔYwcc and B12ΔSlr R were constructed from a biofilm-producing Bacillus subtilis strain B12. Then, the impacts of strain B12 and its high biofilm-producing mutant strain B12ΔYwcc and low biofilmproducing mutant strain B12ΔSlr R on Cd availability and uptake in Chinese cabbage and the related mechanisms were investigated in the Cd-polluted soil. Strain B12 and its mutants B12ΔYwcc and B12ΔSlr R increased the dry biomasses of edible tissues by 54%–130% compared with the controls. Strain B12 and its mutant B12ΔYwcc reduced the soil available Cd content by 36%–50% and root and edible tissue Cd contents by 23%–50% compared with the controls. Furthermore, the mutant strain B12ΔYwcc reduced the edible tissue Cd content by40% and increased the polysaccharide content by 23%, invertase activity by 139%, and gene copies of the cum A by 4.5-fold, eps A by 7.1-fold, and cad A by 4.3-fold, which were involved in Cd adsorption in the rhizosphere soils, respectively, compared with strain B12. The polysaccharide content and cum A, eps A, and cad A gene copy numbers showed significantly reverse correlations with the available Cd content. Notably, the mutant strain B12ΔYwcc showed better ability to colonize the vegetable root surface than strain B12. These findings demonstrated that the biofilm-overproducing mutant strain B12ΔYwcc increased the polysaccharide production and Cd-immobilizing related cum A, eps A, and cad A gene copies, resulting in lower Cd availability and accumulation in Chinese cabbage in the Cd-polluted soil.展开更多
基金financially supported by the grants from the Inter-governmental International Cooperation Special Project of National Key R&D Program of China(2019YFE0114200)the Natural Science Foundation Project of Science and Technology Department of Jilin Province,China(20200201215JC).
文摘Sclerotinia stem rot,caused by Sclerotinia sclerotiorum,is a destructive soil-borne disease leading to huge yield loss.We previously reported that Klebsiella variicola FH-1 could degrade atrazine herbicides,and the vegetative growth of atrazine-sensitive crops(i.e.,soybean)was significantly increased in the FH-1-treated soil.Interestingly,we found that FH-1 could promote soybean growth and induce resistance to S.sclerotiorum.In our study,strain FH-1 could grow in a nitrogen-free environment,dissolve inorganic phosphorus and potassium,and produce indoleacetic acid and a siderophore.The results of pot experiments showed that K.variicola FH-1 promoted soybean plant development,substantially improving plant height,fresh weight,and root length,and induced resistance against S.sclerotiorum infection in soybean leaves.The area under the disease progression curve(AUDPC)for treatment with strain FH-1 was significantly lower than the control and was reduced by up to 42.2%within 48 h(P<0.001).Moreover,strain FH-1 rcovered the activities of catalase,superoxide dismutase,peroxidase,phenylalanine ammonia lyase,and polyphenol oxidase,which are involved in plant protection,and reduced malondialdehyde accumulation in the leaves.The mechanism of induction of resistance appeared to be primarily resulted from the enhancement of transcript levels of PR10,PR12,AOS,CHS,and PDF1.2 genes.The colonization of FH-1 on soybean root,determined using CLSM and SEM,revealed that FH-1 colonized soybean root surfaces,root hairs,and exodermis to form biofilms.In summary,K.variicola FH-1 exhibited the biological control potential by inducing resistance in soybean against S.sclerotiorum infection,providing new suggestions for green prevention and control.
文摘Among the diverse soil bacteria, plant growth promoting rhizobacteria (PGPR) mark an important role in enhancing plant growth through a range of beneficial functions. This is mainly achieved by effective rhizosphere colonization by PGPR. Biofilm development by PGPR is considered as a survival strategy over the planktonic mode of growth under stress and natural conditions. Since the performance of microbial inoculants under field conditions is not always consistent due to various biotic and abiotic factors affecting survival, colonization and functions. Therefore, the rhizobacteria with efficient colonization ability and exhibiting multiple PGP traits are expected to perform better. We hypothesized that the biofilm forming ability of PGPR on plant root will be an added advantage to rhizosphere colonization. Therefore, we have selected a promising isolate of PGPR through random screening programme from rhizoplane of wheat (Triticum aestivum). The selection was based on biofilm development ability, multifarious PGP activities (production of indole acetic acid, sidero-phore, phosphate solubilization, hydrogen cyanide, ammonia production and biocontrol activity) and tolerance to salinity and heavy metals. The selected isolate was identified by 16 s rRNA partial gene sequencing as Pseudomonas entomophila-FAP1. The strain FAP1 formed strong biofilm in microtitre plate, glass surface as well as on the roots of wheat seedlings. Biofilm forming capacity of the FAP1 was characterized by scanning electron microscopy and confocal laser scanning microscopy. FAP1 exhibited biofilm-related traits such as the production of exopolysaccharides, EPS (1501.33 ± 1.08 μg ml-1), alginate (212.81 ± 1.09 μg ml-1), swarming motility (22 ± 1.36 mm), swimming motility (31 ± 2.12 mm) and cell surface hydrophobicity (63%). Rhizosphere colonization by FAP1 was found 7.5 Log CFU g-1 of soil comparable with rhizoplane colonization (7.2 Log CFU g-1 of root). Therefore, biofilm formation on plant roots by promising PGPR may be included as an additional criterion to select a better rhizosphere colonizer. Further, study with mutant deficient in biofilm should be developed for comparative study to explore the exact contribution of biofilm in root colonization under natural soil-plant system.
基金supported by grants from the National Basic Research(973) Program of China(2015CB755700)the National High-Tech R&D(863) Program of China (2012AA02A703)+2 种基金the National Natural Science Foundation of China(31170081)the Special Fund for Agro-scientific Research in the Public Interest,China(201103007)the Guangdong Innovative and Entrepreneurial Research Team Program,China(2013S033).
文摘Flagellar biosynthesis and motility are subject to a four-tiered transcriptional regulatory circuit in Pseudomonas,and the master regulator FleQ appears to be the highest-level regulator in this hierarchical regulatory cascade.Pseudomonas stutzeri A1501 is motile by a polar flagellum;however,the motility and regulatory mechanisms involved in this process are unknown.Here,we searched the A1501 genome for flagella and motility genes and found that approximately 50 genes,which were distributed in three non-contiguous chromosomal regions,contribute to the formation,regulation and function of the flagella.The non-polar mutation of fleQ impaired flagellar biosynthesis,motility and root colonization but enhanced biofilm formation.FleQ positively regulates the expression of flagellar class Ⅱ-Ⅳ genes,suggesting a regulatory cascade that is coordinated similar to that of the well-known P.aeruginosa.Based on our results,we propose that flagellar genes in P.stutzeri A1501 are regulated in a cascade regulated by FleQ and that flagellum-driven motility properties may be necessary for competitive rhizosphere colonization.
基金The national natural Science Foundation of China under contract no.41076089
文摘The colonization features of periphytic diatoms were studied in coastal waters of the Yellow Sea, northern China from May to June 2010, using glass slides as an artificial substratum. Samples were collected at a time interval of 1, 3, 7, 10, 14, 21 and 28 d from two depths of 1 and 3 m. The dynamics of diatom colonization process had a similar pattern in community structure and fitted the logistic model in growth curve at both depths. The maximum abundance and the time for reaching 50% maximum abundance （10 d） showed no significant differences （P〉0.05） between two depths 1 and 3 m. Although the diatom communities repre- sented similar taxonomic composition, they differed in the temporal pattern of structural parameters and in succession dynamics of dominant species between the two layers. The species richness showed significantly higher values during the colonization period more than 14 d, while the species diversity and evenness rep- resented a higher variability with significantly different values （P〈0.05） at a depth of 1 m than at a deeper layer. The results suggest that the diatom colonization follows the logistic model growth curve and differs in colonization features between different depths in the coastal waters, and that the sampling strategy at i m is more effective to detect the ecological features for bioassessment in marine ecosystems.
文摘Aim Dental biofilms are complex communities composed largely of harmless bacteria. Certain pathogenic species including Streptococcus mutans （S. mutans） can become predominant when host factors such as dietary sucrose intake imbalance the biofilm ecology. Current approaches to control S. mutans infection are not pathogen-specific and eliminate the entire oral community along with any protective benefits provided. Here, we tested the hypothesis that removal of S. mutans from the oral community through targeted antimicrobial therapy achieves protection against subsequent S. mutans colonization. Methodology Controlled amounts of S. mutans were mixed with S. mutans-free saliva, grown into biofilms and visualized by antibody staining and cfu quantization. Two specifically-targeted antimicrobial peptides （STAMPs） against S. mutans were tested for their ability to reduce S. mutans biofilm incorporation upon treatment of the inocula. The resulting biofilms were also evaluated for their ability to resist subsequent exogenous S. mutans colonization. Results S. mutans colonization was considerably reduced （9 ± 0.4 fold reduction, P=0.01） when the surface was preoccupied with saliva-derived biofilms. Furthermore, treatment with S. mutans-specific STAMPs yielded S. mutans-deficient biofilms with significant protection against further S. mutans colonization （5 minutes treatment： 38 ± 13 fold reduction P=0.01; 16 hours treatment： 96 ± 28 fold reduction P=0.07）. Conclusion S. mutans infection is reduced by the pre- sence of existing biofilms. Thus maintaining a healthy or ＂normal＂ biofilm through targeted antimicrobial therapy （such as the STAMPs） could represent an effective strategy for the treatment and prevention of S. mutans colonization in the oral cavity and caries progression.
基金supported by the National Natural Science Foundation of China (No. 41977199)the Social Development Program of Jiangsu Province (No. BE2016744)。
文摘Biofilm-producing bacteria can decrease Cd uptake in vegetables, but mechanisms underlying this effect are poorly characterized. In this study, two mutant strains B12ΔYwcc and B12ΔSlr R were constructed from a biofilm-producing Bacillus subtilis strain B12. Then, the impacts of strain B12 and its high biofilm-producing mutant strain B12ΔYwcc and low biofilmproducing mutant strain B12ΔSlr R on Cd availability and uptake in Chinese cabbage and the related mechanisms were investigated in the Cd-polluted soil. Strain B12 and its mutants B12ΔYwcc and B12ΔSlr R increased the dry biomasses of edible tissues by 54%–130% compared with the controls. Strain B12 and its mutant B12ΔYwcc reduced the soil available Cd content by 36%–50% and root and edible tissue Cd contents by 23%–50% compared with the controls. Furthermore, the mutant strain B12ΔYwcc reduced the edible tissue Cd content by40% and increased the polysaccharide content by 23%, invertase activity by 139%, and gene copies of the cum A by 4.5-fold, eps A by 7.1-fold, and cad A by 4.3-fold, which were involved in Cd adsorption in the rhizosphere soils, respectively, compared with strain B12. The polysaccharide content and cum A, eps A, and cad A gene copy numbers showed significantly reverse correlations with the available Cd content. Notably, the mutant strain B12ΔYwcc showed better ability to colonize the vegetable root surface than strain B12. These findings demonstrated that the biofilm-overproducing mutant strain B12ΔYwcc increased the polysaccharide production and Cd-immobilizing related cum A, eps A, and cad A gene copies, resulting in lower Cd availability and accumulation in Chinese cabbage in the Cd-polluted soil.
