昆虫的抗菌蛋白及其利用

从种的数目和个体数目来看,昆虫在当今地球上是最为繁荣的一类生物,遍布于地球的陆、水、空各处。昆虫能保持如此繁荣,是因为它具有优于其他生物种的生殖能力、活体防御能力等。昆虫的活体防御机能有多种,其中作为体液防御因子之一的抗菌蛋白倍受人们注目,在此领域开展了多方面的研究,取得了可喜的成果。同时随着抗菌蛋白结构和编码基因的解析以及在分子生物学水平上改变抗菌蛋白研究的深入,昆虫抗菌蛋白在医药、农业等方面的利用也显示出良好的前景。本文中我们就已分离得到的昆虫主要抗菌蛋白及其作用机理和利用前景作一简要论述。…     

昆虫黑化现象

昆虫黑化是自然界中普遍存在的一种多型现象,也成为揭示物种在自然界中进化与适应的经典范例。昆虫黑化形成的原因与类别多种多样,黑化的遗传调控和分子基础也各不相同。本文根据国外黑化昆虫研究取得的主要进展,结合我国东方粘虫Mythimna separata种群中发生的黑化现象,对昆虫黑化的形成原因、类别、遗传调控、生物学变异以及黑化的分子基础等方面研究现状进行了概述,并对该领域的未来研究热点进行探讨。     

昆虫微生物组:昆虫健康和适应的守护者

正昆虫是自然界分布最为广泛,数量最多,种类也最为繁盛的动物类群。在经历了无数地质变迁之后,昆虫仍然成功生存在这个星球。在探究昆虫成功秘诀的过程中,研究人员发现昆虫除了自身独特的结构和功能以外,它们在长期进化过程中与微生物形成了复杂多样的共生关系。正是     

中国食蚜蝇科昆虫研究进展

食蚜蝇Syrphidae是双翅目昆虫中一类很重要的资源昆虫和天敌昆虫,在控制蚜虫、自然界传粉等方面有很重要的作用,同时也是仿生学等研究的重要实验材料。文章介绍国内食蚜蝇科昆虫最近几年的分类学、生态学、生物学习性及生物防治的研究现状。     

昆虫多样性的保护现状与趋势

昆虫是自然界中种类最多的动物,在生态系统中具有重要的作用,但是昆虫在生物多样性保护中没有受到应有的重视.多个实例证明,很多昆虫种类处在数量下降甚至绝灭的状态.究其原因,人类的认识不足是导致昆虫多样性保护未受重视的主要原因,栖息地破坏是昆虫濒危的主要原因.由于昆虫生活史的特殊性,其保护策略与大型动物的保护有很大不同.昆虫多样性的保护可以与人类活动共存.     

昆虫共生微生物在病虫害和疾病控制上的应用前景

昆虫与微生物之间的互利共生关系是自然界中一种常见的互作形式。昆虫的种类丰富多样并且在自然界中分布广泛,在一定程度上得益于共生微生物的帮助。随着生物技术的不断发展,越来越多的共生微生物和互利共生模式得以发现并深入研究。微生物不仅能够为昆虫的生长发育提供营养,还能合成很多生物活性物质、调节宿主的免疫、对抗捕食者和抵御病原微生物感染,成为宿主昆虫健康和适应的守护者。鉴于共生微生物与昆虫生理生态的密切联系,以及昆虫对人类经济与健康的重要影响,利用共生微生物对昆虫及虫媒病进行生物控制已经成为一个热点研究方向,并展现了良好的应用前景。本文对昆虫共生微生物的多样性、生物学功能、与宿主相互作用机制及其在病虫害和虫媒病防治中的研究进展进行综述和展望。     

浅谈昆虫标本馆工作

<正> 一、昆虫标本馆概况 (一)昆虫标本馆的性质 昆虫标本馆保存的多数是“干制”的昆虫个体标本,是自然界昆虫的基本缩影,是研究昆虫区系的基本库。 按照国际动物命名法规,发表一个新种时,只能从其两性中各选一具有代表性的个体分别     

昆虫体色分化研究进展

昆虫体色分化现象在自然界中普遍存在,它给昆虫的分类等工作带来了不便。文章介绍了寄主专化论、环境因素控制论、基因控制论等有关昆虫体色分化机理的3个不同观点,着重从染色体和基因方面介绍了昆虫体色分化的研究,以及分子标记技术在其研究中的应用,并对昆虫体色分化的研究方向进行了展望。     

高原环境和昆虫的适应

<正> 西藏地区由于高原强烈抬升,出现了巨大的高差。不同海拔高度有着不同的生境,昆虫在不同的生境下,有着不同的适应性。 生活在低海拔常绿阔叶林内的昆虫,其周围环境比较稳定,温暖潮湿,食物充足,生活中突出的矛盾是天敌的侵害。自然界中弱肉强食互相竞争的现象在低海拔的阔叶林带内表现得更为突出,小昆虫受大中型昆虫攻击,大型动物可以捕食大中型昆虫,而小型昆虫也可以通过各种方式如寄生、传病等危害大型动物和大中型昆虫。它们之间互相制约,互相渗透。竞争激烈(如图1)。我们所指的这种关系,仅是自然界中动物间的关系的一方面,除此之外当然还有共生及辅助关系,但在此我们主要是分析竞争与低海拔昆虫适应性的关系。这种物种间互相竞争似乎是消积的表     

生命的延续

彩蝶萦绕花间,翩翩起舞,美好的爱情故事似乎在自然界也上演着。然而,自然界中求偶的竞争远没有我们想像的这样美好与浪漫,所有昆虫都拼尽全力,为的就是能够让自己的基因得以延续。     

Drosophila males transfer antibacterial proteins from their accessory gland and ejaculatory duct to their mates

The male fruitfly, Drosophila melanogaster, transfers to his mate proteins that increase his reproductive success by causing changes in her behavior and physiology. Here we show that among the transferred proteins are ones with antibacterial activity. We performed Escherichia coli overlay assays of native PAGE or renatured SDS-PAGE of reproductive tissue extracts of wild-type or transgenic males deficient in accessory gland function. We detected a 28 kDa male accessory gland-derived protein and two ejaculatory duct-derived proteins all with antibacterial activity. Based on its gel mobility and tissue of synthesis, one of the ejaculatory duct proteins is likely to be andropin, a previously-reported 6 kDa antibacterial peptide. All three proteins are transferred to females during mating. Therefore, they could assist in protecting the male's reproductive tract and, after transfer to the female, the female's reproductive tract or eggs against bacterial infection. Since seminal fluid proteins are transferred before the sperm, these antibacterial proteins may also protect sperm from bacterial infection.     

Lipid Requirement for the Lipase Production by Geotrichum candidum Link

The injection of live or heat-killed bacteria into larvae of the silkworm, Bombyx mori, induced antibacterial activity in the hemolymph. A wide variety of gram-negative and gram-positive bacteria were effective as inducing agents, but saline alone, yeast cells and fungal spores were not effective. The antibacterial activities were separated into six bands on native polyacrylamide gel electrophoresis, which were sensitive to trypsin. Some of these antibacterial proteins were partially purified by CM-cellulose column chromatography. The proteins were heat-stable and showed no lysozyme activity. The proteins repressed the growth of various gram-positive and gram-negative bacteria.     

A novel Rel protein and shortened isoform that differentially regulate antibacterial peptide genes in the silkworm Bombyx mori

Two cDNAs encoding novel Rel proteins were cloned from the silkworm, Bombyx mori. These cDNA clones (BmRelA and BmRelB) showed identical nucleotide sequences except for the 5'-region. BmRelB cDNA derived probably from an alternatively spliced mRNA lacked 241 bp nucleotides at the 5'-region of the BmRelA cDNA, resulting in a loss of the first 52 amino acids. Expression of antibacterial peptide genes was strongly inhibited upon infection with Micrococcus luteus in transgenic silkworms in which BmRel gene expression was knocked down, suggesting that these two Rel proteins are involved in activation of antibacterial peptide genes. Co-transfection experiments indicated that BmRelB activated the Attacin gene strongly and other genes to a lesser extent, whereas BmRelA activated Lebocin 4 gene strongly and Attacin and Lebocin 3 genes very weakly. The Rel homology domain of BmRelA and BmRelB was shown to bind specifically to kappaB sites of antibacterial peptide genes. Proline-rich domains of the BmRels were necessary for activation of antibacterial peptide genes. These results illustrate that a minor structural change in Rel proteins can provoke a dramatic differential activation of antibacterial peptide genes, suggesting a novel regulatory mechanism for insect antibacterial peptide gene expression.     

Purification of sarcotoxin II, antibacterial proteins of Sarcophaga peregrina (flesh fly) larvae

Three antibacterial proteins with almost identical primary structures termed sarcotoxin IIA, IIB, and IIC were purified to homogeneity from the hemolymph of third instar larvae of Sarcophaga peregrina. The molecular masses of these proteins were about 24,000. These proteins were found to have common antigenicity, and antibody against sarcotoxin IIA cross-reacted with sarcotoxin IIB and IIC. Radioimmunoassay using this antibody showed that these proteins are induced in the hemolymph in response to injury of the larval body wall.     

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.     

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.     

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.     

Characterization of six antibacterial response genes from the European corn borer (Ostrinia nubilalis) larval gut and their expression in response to bacterial challenge

Six cDNAs encoding putative antibacterial response proteins were identified and characterized from the larval gut of the European corn borer (Ostrinia nubilalis). These antibacterial response proteins include four peptidoglycan recognition proteins (PGRPs), one β-1,3-glucanase-1 (βglu-1), and one lysozyme. Tissue-specific expression analysis showed that these genes were highly expressed in the midgut, except for lysozyme. Analysis of expression of these genes in different developmental stage showed that they were expressed in larval stages, but little or no detectable expression was found in egg, pupa and adult. When larvae were challenged with Gram-negative bacteria (Enterobacter aerogenes), the expression of all six genes was up-regulated in the fatbodies. However, when larvae were challenged with Gram-positive bacteria (Micrococcus luteus), only PGRP-C and lysozyme genes were up-regulated. This study provides additional insights into the expression of antibacterial response genes in O. nubilalis larvae and helps us better understand the immune defense response in O. nubilalis.     

Thrombocidins, microbicidal proteins from human blood platelets, are C-terminal deletion products of CXC chemokines

Antibacterial proteins are components of the innate immune system found in many organisms and produced by a variety of cell types. Human blood platelets contain a number of antibacterial proteins in their alpha-granules that are released upon thrombin activation. The present study was designed to purify these proteins obtained from human platelets and to characterize them chemically and biologically. Two antibacterial proteins were purified from platelet granules in a two-step protocol using cation exchange chromatography and continuous acid urea polyacrylamide gel electrophoresis and were designated thrombocidin (TC)-1 and TC-2. Characterization of these proteins using mass spectrometry and N-terminal sequencing revealed that TC-1 and TC-2 are variants of the CXC chemokines neutrophil-activating peptide-2 and connective tissue-activating peptide-III, respectively. TC-1 and TC-2 differ from these chemokines by a C-terminal truncation of 2 amino acids. Both TCs, but not neutrophil-activating peptide-2 and connective tissue-activating peptide-III, were bactericidal for Bacillus subtilis, Escherichia coli, Staphylococcus aureus, and Lactococcus lactis and fungicidal for Cryptococcus neoformans. Killing of B. subtilis by either TC appeared to be very rapid. Because TCs were unable to dissipate the membrane potential of L. lactis, the mechanism of TC-mediated killing most probably does not involve pore formation.     

Insect antibacterial proteins: not just for insects and against bacteria.

In response to a bacterial infection, insects launch an array of countermeasures. Among these are the antibacterial proteins, which effectively lyse bacteria or are bacteriostatic. These proteins were generally assumed to be restricted to insects, yet recent information has shown some homologous counterparts in vertebrates, including humans. Recent data have revealed that at least some of these proteins can also act against eukaryotic cells, including human infectious parasites. The latter activities have opened up new possibilities for disease control.