Purification and Partial Characterization of an Antibacterial Protein Tz1

A strain (T3) of Bacillus has been screened from paddy field. It secretes large amount of antibacterialproteins which show a strong inhibiting activity against several pathogens of rice. This paper presentsa systematic study of the inhibition spectrum and characteristics of T3 proteins. Total proteins wereprecipitated with ammonium sulfate at 70% saturation from cell-free culture. One of the proteins(Tzl) was purified from the crude extracts with Sephadex G-100, DEAE52 and FPLC Superose 12columns. A single band was demonstrated in both 15% SDS-PAGE and IEF, with an apparent MWof 6,9 kd and a pI of 7.8. Its amino acid composition was analyzed and part of its sequence,determined.     

The antibacterial activity of peptides derived from human beta-2 glycoprotein I is inhibited by protein H and M1 protein from Streptococcus pyogenes

During the last years, the importance of antibacterial peptides has attracted considerable attention. We report here that peptides derived from the fifth domain of beta-2 glycoprotein I (beta(2)GPI), a human heparin binding plasma protein, have antibacterial activities against Gram-positive and Gram-negative bacteria. Streptococcus pyogenes, an important human pathogen that can survive and grow in human blood, has developed mechanisms to escape the attack by these peptides. Thus, protein H and M1 protein, two surface proteins of the highly pathogenic S. pyogenes AP1 strain, bind full-length beta(2)GPI and thereby prevent the processing of beta(2)GPI by proteases from polymorphonuclear neutrophils (PMNs) into antibacterial peptides. In addition, protein H and M1 protein, released from the bacterial cell wall by PMN-derived proteases, bind to, and inhibit the activity of, beta(2)GPI-derived antibacterial peptides. Taken together, the data suggest that the interaction between the streptococcal proteins and beta(2)GPI or beta(2)GPI-derived peptides presents a novel mechanism to resist an antibacterial attack by beta(2)GPI-cleavage products.     

草珊瑚炭疽病拮抗细菌的鉴定及其抑菌机理

【背景】草珊瑚炭疽病发生严重,目前尚未有植物内生细菌对该病原菌生物防治的研究报道。【目的】筛选对肿节风炭疽病Colletotrichumdematium具有拮抗作用的内生细菌,并对其抑菌机理进行研究。【方法】采用平板稀释法从广西不同地区采集健康肿节风植株的不同组织分离、纯化获得内生细菌。【结果】平板对峙试验结果表明,来自茎的RJ-4和JJ-5对草珊瑚炭疽病具有较强的拮抗作用,其中拮抗作用最强的菌株是RJ-4,其抑制率达到84.10%。抗菌谱测定结果表明,RJ-4、JJ-5对供试的14种病原真菌均有明显的拮抗效果,拮抗作用最强的是RJ-4,平均抑制率达到95.30%;抑菌机理研究结果表明,该菌株可以分泌蛋白酶和纤维素酶以及几丁质酶,破坏病菌菌丝,抑制病菌生长;含有拮抗细菌的发酵液对病原菌菌丝抑制明显,菌丝扭曲、断裂且分枝缠绕、菌丝颜色加深等。通过形态学特性和16S rRNA基因鉴定,RJ-4菌株为解淀粉芽孢杆菌(Bacillus amyloliquefaciens)。【结论】RJ-4菌株具有抑菌抗病功能,并能产生多种抗菌活性物质,这可为新型抗菌物质提供资源。     

The novel rice (Oryza sativa L.) gene OsSbf1 encodes a putative member of the Na+/bile acid symporter family

PCR-based differential screening was used to identify ethylene-induced genes in deep-water rice (Oryza sativa L.). One of the isolated cDNAs represented a novel protein, OsSBF1, with high homology to mammalian Na+/bile acid transporters and to sodium-dependent transporters from bacteria. One highly homologous protein and three less conserved homologues were identified in Arabidopsis thaliana indicating that Sbf proteins exist in monocot and dicot plant species. Expression of OsSbf1 in deep-water rice was shown to be elevated by growth-inducing treatments. Since bile acids have not been found in plants to date a possible function of SBF proteins may be in the transport of structurally related sulphonated brassinosteroids.     

Pore-forming properties and antibacterial activity of proteins extracted from epidermal mucus of fish.

Among several biological functions, the epidermal mucus of fish may play an important role in host defense, particularly in the prevention of colonization by parasites, bacteria and fungi. In previous work, two hydrophobic proteins of 27 and 31 kDa were isolated from carp mucus. This study identified a strong antibacterial activity (0.16-0.18 microM) well correlated with pore-forming properties. Here this work was extended to other fish species, four fresh water fish and one sea water fish. After a first step of purification, water-soluble and hydrophobic material were separated, and both fractions were analyzed by SDS-PAGE and capillary electrophoresis. Only the hydrophobic component induced pore-forming activity, when reconstituted in planar lipid bilayers. This pore-forming activity was well correlated to a strong antibacterial activity against several bacteria strains. These results suggest that fish secrete antibacterial proteins able to permeabilize the membrane of the target cell and thus act as a defense barrier.     

Separation and purification of a potent bactericidal/permeability-increasing protein and a closely associated phospholipase A2 from rabbit polymorphonuclear leukocytes. Observations on their relationship.

Two antibacterial proteins from rabbit polymorphonuclear leukocytes, a potent bactericidal cationic protein that increases the envelope permeability of susceptible gram-negative bacteria and a phospholipase A2, have been purified to near homogeneity by ion exchange, gel filtration, and hydrophobic interaction chromatography. The apparently noncatalytic bactericidal/permeability-increasing protein has an approximate molecular weight of 50,000 and is isoelectric at pH 9.5 to 10.0. The molecular properties, including amino acid composition, and the antibacterial potency and specificity of this rabbit leukocyte protein and of the bactericidal/permeability-increasing protein from human granulocytes that we have recently purified (J. Biol. Chem. 253, 2664-2672, 1978) are closely similar. Both proteins kill several strains of Escherichia coli and Salmonella typhimurium. Rough strains are more sensitive than smooth strains. All gram-positive bacterial species tested are insensitive to high concentrations of either rabbit or human protein. The phospholipase A2, purified by hydrophobic interaction chromatography on phenyl-Sepharose, ran as a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis with an apparent molecular weight of 14,000 and had a specific enzymatic activity comparable to that of purified phospholipases A2 from other sources. Separation of the phospholipase A2 from the bactericidal/permeability-increasing protein has no noticeable effect on the bactericidal and permeability-increasing activities of the purified bactericidal protein, but removes the ability of the phospholipase A2 to hydrolyze the phospholipids of intact Escherichia coli. Upon recombination of the phospholipase A2 with the bactericidal/permeability-increasing protein, the phospholipase A2 regains its activity toward the phospholipids of intact E. coli suggesting that these two antibacterial leukocyte proteins act in concert.     

Purification of three antibacterial proteins from the culture medium of NIH-Sape-4, an embryonic cell line of Sarcophaga peregrina

Three antibacterial proteins were purified from the culture medium of NIH-Sape-4, an embryonic cell line of Sarcophaga peregrina (flesh fly). Sequencing studies showed that two of these proteins belong to the sarcotoxin I family, potent antibacterial proteins purified from the hemolymph of Sarcophaga larvae, whereas the other protein, named sapecin, is a new protein consisting of 40 amino acid residues including 6 cysteine residues. Unlike sarcotoxin I, sapecin preferentially represses the growth of various Gram-positive bacteria. The proteins of the sarcotoxin I family produced by this cell line were found to have carboxyl-terminal glycine, whereas sarcotoxin I in the hemolymph has amidated amino acids. This suggests that the embryonic cells lack an enzyme that cleaves off carboxyl-terminal glycine to form a new amidated carboxyl terminus.     

Rice dehydrin K-segments have <Emphasis Type="Italic">in vitro</Emphasis> antibacterial activity

Dehydrins are groups of plant proteins that have been shown to response to various environmental stimuli such as dehydration, elevated salinity, and low temperature. However, their roles in plant defense against microbes have not been demonstrated. In an attempt to discover plant antimicrobial proteins, we have screened a rice cDNA library and isolated several cDNAs coding for dehydrins. Protein extracts from Escherichia coli expressing these cDNAs were tested for their activity against Gram-positive bacteria (Bacillus pumilus, B. subtilis, Staphylococcus aureus, and Sarcina lutea) and Gramnegative bacteria (Escherichia coli and Xanthomonas oryzae pv. oryzae). The results indicate that the crude protein extracts exhibited antibacterial activities against the Gram-positive bacteria. However, dehydrins purified by immunoaffinity chromatography were not active against the bacteria. To pinpoint the dehydrin peptides that were responsible for the bactericidal activity, we expressed DNA sequences coding for truncated dehydrins containing either K- or S-segment and found that K-segment peptides, and not S-segment, were responsible for the antibacterial activities against Gram-positive bacteria. Antibacterial assay with synthetic K-segments indicated that the peptides inhibited growth of B. pumilus with minimum inhibition concentration and minimum bactericidal concentration of 130 and 400 μg/ml, respectively.     

XadM, a novel adhesin of Xanthomonas oryzae pv. oryzae, exhibits similarity to Rhs family proteins and is required for optimum attachment, biofilm formation, and virulence

By screening a transposon-induced mutant library of Xanthomonas oryzae pv. oryzae, the bacterial blight pathogen of rice, we have identified a novel 5.241-kb open reading frame (ORF) named xadM that is required for optimum virulence and colonization. This ORF encodes a protein, XadM, of 1,746 amino acids that exhibits significant similarity to Rhs family proteins. The XadM protein contains several repeat domains similar to a wall-associated surface protein of Bacillus subtilis, which has been proposed to be involved in carbohydrate binding. The role of XadM in X. oryzae pv. oryzae adhesion was demonstrated by the impaired ability of an xadM mutant strain to attach and form biofilms. Furthermore, we show that XadM is exposed on the cell surface and its expression is regulated by growth conditions and plays an important role in the early attachment and entry inside rice leaves. Interestingly, XadM homologs are present in several diverse bacteria, including many Xanthomonas spp. and animal-pathogenic bacteria belonging to Burkholderia spp. This is the first report of a role for XadM, an Rhs family protein, in adhesion and virulence of any pathogenic bacteria.     

Isolation of endophytic bacteria from rice and assessment of their potential for supplying rice with biologically fixed nitrogen

The extension of nitrogen-fixing symbioses to important crop plants such as the cereals has been a long-standing goal in the field of biological nitrogen fixation. One of the approaches that has been used to try to achieve this goal involves the isolation and characterization of stable endophytic bacteria from a variety of wild and cultivated rice species that either have a natural ability to fix nitrogen or can be engineered to do so. Here we present the results of our first screening effort for rice endophytes and their characterization using acetylene reduction assays (ARA), genomic fingerprinting with primers corresponding to naturally occurring repetitive DNA elements (rep-PCR), partial 16S rDNA sequence analysis and PCR mediated detection of nitrogen fixation (nif) genes with universal nif primers developed in our laboratory. We also describe our efforts to inoculate rice plants with the isolates obtained from the screening, in order to examine their invasiveness and persistence (stable endophytic maintenance). Lastly, we review our attempts to tag selected isolates with reporter genes/proteins, such as beta-glucuronidase (gus) or green fluorescent protein (gfp), in order to be able to track putative endophytes during colonization of rice tissues.     

Isolation of two isoforms of a novel 15-kDa protein from rabbit polymorphonuclear leukocytes that modulate the antibacterial actions of other leukocyte proteins

We have recently reported the use of the highly selective and reversible binding of the potent bactericidal/permeability-increasing protein (BPI) to target Gram-negative bacteria (Escherichia coli) for its isolation from crude extracts of human polymorphonuclear leukocytes (PMN). We now report the use of the same procedure for the purification from rabbit PMN of BPI and also of a novel 15-kDa species that consists of two nearly identical isoforms. These 15-kDa proteins have no demonstrable antibacterial activities by themselves. However, one isoform (p15A) potentiates strongly and the other (p15B) weakly the early antibacterial effects of both rabbit and human BPI. Both isoforms inhibit the late lethal action of BPI. Whereas the potentiating effect is specific for BPI the inhibitory effect is seen also with another antibacterial protein of PMN granules, azurocidin. Thus, we have identified in rabbit PMN a previously unrecognized 15-kDa protein species that may modulate during phagocytosis the antimicrobial effects of BPI (and other granule proteins).     

新型乳杆菌素产生菌的筛选及菌株特性的研究

从酸菜汁中分离出 2 4株乳酸杆菌 ,采用牛津杯定量扩散法筛选出 1株抑菌活性较高的乳酸杆菌 ,经鉴定为戊糖乳杆菌。排除乳酸对指示菌作用的干扰 ,该菌株的离心发酵液不仅对革兰氏阳性细菌有抑制作用 ,而且对大肠杆菌 (E .coli.) ,沙门氏菌 (Salmonellatyphi)等革兰氏阴性细菌也有一定的抑制作用     

Isolation, structure and antibacterial activity of pleosporone from a pleosporalean ascomycete discovered by using antisense strategy

Protein synthesis is one of the best antibacterial targets that have led to the development of a number of highly successful clinical drugs. Protein synthesis is catalyzed by ribosome, which is comprised of a number of ribosomal proteins that help the catalysis process. Ribosomal protein S4 (RPSD) is one of the proteins that is a part of the ribosomal machinery and is a potential new target for the discovery of antibacterial agents. Screening of microbial extracts using antisense-sensitized rpsD Staphylococcus aureus strain led to the isolation of pleosporone, a new compound, with modest antibacterial activities with MIC ranging from 1 to 64 microg/mL. This compound showed the highest sensitivity for Streptococcus pneumoniae and Haemophilus influenzae, and exhibited MIC's of 4 and 1 microg/mL, respectively. Pleosporone showed modest selectivity for the inhibition of RNA synthesis compared to DNA and protein synthesis, and showed activity against HeLa cells. Isolation, structure elucidation, and biological activity of pleosporone have been described.     

Exploring the plant transcriptome through phylogenetic profiling

Publicly available protein sequences represent only a small fraction of the full catalog of genes encoded by the genomes of different plants, such as green algae, mosses, gymnosperms, and angiosperms. By contrast, an enormous amount of expressed sequence tags (ESTs) exists for a wide variety of plant species, representing a substantial part of all transcribed plant genes. Integrating protein and EST sequences in comparative and evolutionary analyses is not straightforward because of the heterogeneous nature of both types of sequence data. By combining information from publicly available EST and protein sequences for 32 different plant species, we identified more than 250,000 plant proteins organized in more than 12,000 gene families. Approximately 60% of the proteins are absent from current sequence databases but provide important new information about plant gene families. Analysis of the distribution of gene families over different plant species through phylogenetic profiling reveals interesting insights into plant gene evolution, and identifies species- and lineage-specific gene families, orphan genes, and conserved core genes across the green plant lineage. We counted a similar number of approximately 9,500 gene families in monocotyledonous and eudicotyledonous plants and found strong evidence for the existence of at least 33,700 genes in rice (Oryza sativa). Interestingly, the larger number of genes in rice compared to Arabidopsis (Arabidopsis thaliana) can partially be explained by a larger amount of species-specific single-copy genes and species-specific gene families. In addition, a majority of large gene families, typically containing more than 50 genes, are bigger in rice than Arabidopsis, whereas the opposite seems true for small gene families.     

粉纹夜蛾离体细胞抗菌肽的抗菌谱测定

用热灭活的大肠杆菌DHSQ诱导粉纹夜蛾(Trichoplusia ni)离体细胞产生抗菌肽,用三氯乙酸沉淀法提取出该活性物质,采用琼脂糖孔穴扩散法和生长抑制测定法测定其抗菌谱,发现该抗菌物质具有较广的抗微生物活性,其中特别是对革兰氏阴性菌中的沙门氏茵和大肠杆茵,酵母菌中的白色念珠菌,植物病源真茵中的花生白绢病茵和小麦赤霉病茵具有较强的抑菌活性,从而表明该物质是一种既抗细菌,又抗真菌的抗微生物肽。     

Antagonistic activity expressed by Shigella sonnei: identification of a putative new bacteriocin

Bacteriocins are antibacterial, proteinaceous substances that mediate microbial dynamics. Bacteriocin production is a highly disseminated property among all major lineages of bacteria, including Shigella. In this paper, we addressed the purification and characterisation of a bacteriocin produced by a Shigella sonnei strain (SS9) isolated from a child with acute diarrhoea. The substance was purified through ammonium-sulphate precipitation and sequential steps of chromatography. The intracellular fraction obtained at 75% ammonium sulphate maintained activity following exposure to pH values from 1-11 and storage at -80ºC for more than two years and was inactivated by high temperatures and proteases. The molecular mass of the purified bacteriocin was determined by mass spectrometry to be 18.56 kDa. The N-terminal sequence of the bacteriocin did not match any other antibacterial proteins described. A putative new bacteriocin produced by S. sonnei has been detected. This bacteriocin may represent a newly described protein or a previously described protein with a newly detected function. Considering that SS9 expresses antagonism against other diarrhoeagenic bacteria, the bacteriocin may contribute to S. sonnei virulence and is potentially applicable to either preventing or controlling diarrhoeal disease.     

Identification of antibacterial mechanism of L-amino acid oxidase derived from Trichoderma harzianum ETS 323

Although L-amino oxidase (LAAO; EC 1.4.3.2) has been reported to be a potent antibacterial agent, the mechanism responsible for its antibacterial activity has not been identified. The present study aimed to identify the mechanism responsible for the antibacterial activity of Th-LAAO, an LAAO recently isolated from the extracellular proteins of Trichoderma harzianum ETS 323, at the same time as elucidating the nature of this enzyme. The results obtained indicate that the enzyme activity and structure of Th-LAAO are stable at pH 6-8 and less stable at both pH 4-5.5 and pH 9. At pH 7.0, the optimum temperature for Th-LAAO was found to be 40 °C, comprising the temperature at which enzymatic activity is greatest, with enzymatic activity deceasing with further increases in temperature as a result of thermal denaturation of the enzyme, leading to partial denaturation at 50 °C. The results obtained by confocal microscopy and flow cytometry indicate that Th-LAAO interacts with bacteria to cause membrane permeabilization, and this interaction may be promoted by the amphipathic sequence in Th-LAAO and other cytotoxic LAAOs located at the N-terminus. The findings of increased exogenous H(2) O(2) production and reactive oxidative species accumulation in Th-LAAO-treated bacteria indicate that reactive oxidative species accumulation may trigger forms of cell damage, including lipid peroxidation and DNA strand breakage that results in bacterial growth inhibition. Taken together, the results indicate that the processes of bacterial interaction, membrane permeabilization and H(2)O(2) production are involved in the mechanism responsible for the antibacterial activity of Th-LAAO.     

Bacteriocins of gram-positive bacteria.

In recent years, a group of antibacterial proteins produced by gram-positive bacteria have attracted great interest in their potential use as food preservatives and as antibacterial agents to combat certain infections due to gram-positive pathogenic bacteria. They are ribosomally synthesized peptides of 30 to less than 60 amino acids, with a narrow to wide antibacterial spectrum against gram-positive bacteria; the antibacterial property is heat stable, and a producer strain displays a degree of specific self-protection against its own antibacterial peptide. In many respects, these proteins are quite different from the colicins and other bacteriocins produced by gram-negative bacteria, yet customarily they also are grouped as bacteriocins. Although a large number of these bacteriocins (or bacteriocin-like inhibitory substances) have been reported, only a few have been studied in detail for their mode of action, amino acid sequence, genetic characteristics, and biosynthesis mechanisms. Nevertheless, in general, they appear to be translated as inactive prepeptides containing an N-terminal leader sequence and a C-terminal propeptide component. During posttranslational modifications, the leader peptide is removed. In addition, depending on the particular type, some amino acids in the propeptide components may undergo either dehydration and thioether ring formation to produce lanthionine and beta-methyl lanthionine (as in lantibiotics) or thio ester ring formation to form cystine (as in thiolbiotics). Some of these steps, as well as the translocation of the molecules through the cytoplasmic membrane and producer self-protection against the homologous bacteriocin, are mediated through specific proteins (enzymes). Limited genetic studies have shown that the structural gene for such a bacteriocin and the genes encoding proteins associated with immunity, translocation, and processing are present in a cluster in either a plasmid, the chromosome, or a transposon. Following posttranslational modification and depending on the pH, the molecules may either be released into the environment or remain bound to the cell wall. The antibacterial action against a sensitive cell of a gram-positive strain is produced principally by destabilization of membrane functions. Under certain conditions, gram-negative bacterial cells can also be sensitive to some of these molecules. By application of site-specific mutagenesis, bacteriocin variants which may differ in their antimicrobial spectrum and physicochemical characteristics can be produced. Research activity in this field has grown remarkably but sometimes with an undisciplined regard for conformity in the definition, naming, and categorization of these molecules and their genetic effectors. Some suggestions for improved standardization of nomenclature are offered.     

Antimicrobial activity of omwaprin, a new member of the waprin family of snake venom proteins

We have isolated and characterized omwaprin, a 50-amino-acid cationic protein from the venom of inland taipan (Oxyuranus microlepidotus). It is a new member of the waprin family of snake venom proteins. A synthetic gene was designed and constructed for expressing the recombinant protein in Escherichia coli. Recombinant omwaprin was used for carrying out functional analyses. The protein is non-toxic to Swiss albino mice at doses of up to 10 mg/kg when administered intraperitoneally. However, it shows selective and dose-dependant antibacterial activity against Gram-positive bacteria. The minimum inhibitory doses were in the range 2-10 microg for selected species of bacteria in radial diffusion assays. The antibacterial activity is salt-tolerant up to 350 mM NaCl. However, omwaprin lost its antibacterial activity upon reduction and alkylation of its cysteine residues, or upon deletion of six N-terminal amino acid residues, four of which are positively charged. These observations indicate that the three-dimensional structure constrained by four disulfide bonds and the N-terminal residues are essential for its activity. The mechanism of action is via membrane disruption, as shown by scanning electron microscopy. Importantly, omwaprin lacks haemolytic activity on human erythrocytes. This demonstrates the specificity of omwaprin for bacterial membranes. Unlike other reported WAP (whey acidic protein) domain-containing antibacterial proteins, including elafin, EPPIN (epididymal proteinase inhibitor), SWAM1 and SWAM2 [single WAP (whey acidic protein) motif proteins 1 and 2] and SLPI (secretory leucocyte proteinase inhibitor), omwaprin shows species-specific activity on the Gram-positive bacteria tested.     

水稻中cry1Ah1基因密码子优化方案的比较

cry1Ah1基因是本实验室克隆的具有自主知识产权的模式基因,对鳞翅目害虫水稻二化螟等具有高毒力,具有较好的应用前景。为提高cry1Ah1基因在水稻中的表达量,探讨密码子使用频率对基因表达的影响,依据水稻密码子使用频率设计5种不同的优化方案,提高GC含量并去除剪切信号等不稳定因素后合成cry1Ah1基因杀虫活性区域。优化后的基因在大肠杆菌Rosetta(DE3)中正常表达了65 kDa蛋白,表达蛋白对2龄小菜蛾和水稻二化螟初孵幼虫都具有良好的杀虫活性。优化的基因转化水稻日本晴后,PCR阳性率达到87%以上,实时荧光定量RT-PCR和ELISA分析表明全部采用最高频率密码子的优化方案效果最好,Cry1Ah蛋白平均表达量占可溶性蛋白的0.104%。