Effects of antibiotics on hydrogen production and gut symbionts in the Formosan subterranean termite Coptotermes formosanus (Isoptera: Rhinotermitidae)

Abstract Symbiotic microorganisms that inhabit the gut of Coptotermes formosanus enable this termite to degrade lignocelluloses and further produce hydrogen as an important intermediate to be recycled in its hindgut or as a byproduct to be emitted to the atmosphere. Both symbiotic protists and prokaryotes in the guts of termites demonstrated some different roles with respect to hydrogen production. In this study, the effects of two antibiotics, ampicillin and tetracycline, on hydrogen emission and the gut symbionts of C. formosanus were investigated. Hydrogen emission from termite guts was significantly enhanced when termites fed on wood diets treated with either ampicillin or tetracycline. The greatest H₂ emission rates, 2 519 ± 74 and 2 080 ± 377 nmol/h/g body weight, were recorded with the treatments of ampicillin and tetracycline, respectively, which showed 6–7 times more H₂ production than that of controls. Antibiotic‐treated diets negatively affected the prokaryotic communities and reduced their abundances, particularly on those ectosymbionts inhabiting the gut walls or in the gut fluid of C. formosanus, such as spirochetes. However, no significant reductions in the counts of gut cellulolytic protists, Pseudotrichonympha grassii and Holomastigotoids hartmanni, were recorded; and with a further observation by confocal laser scanning microscopy, the endosymbionts inhabiting P. grassii generally survived the antibiotic treatments. These results suggest that some prokaryotes may serve as the main hydrogen consumers, while P. grassii, together with its endosymbionts, may function as the main contributors for hydrogen production in the hindgut of C. formosanus.     

A review on the occurrence and taxonomy of heterotrophic protists in extreme acidic environments of pH values ≤ 3

The occurrence and some important taxonomic problems of heterotrophic protists from extremely acidic (pH 3) environments are briefly discussed. Almost all information on the occurrence of heterotrophic protists from extremely acidic environments is restricted to acid mine drainage (AMD) or streams influenced by AMD. Most of the information is provided for ciliates. Very little information is available on the occurrence of flagellates, rhizopods and heliozoa in this environment. Within the ciliates Urotricha, Vorticella and Oxytricha dominate in acidic mining lakes. Actinophrys sp. is the most important heliozoan in these environments. There are many taxonomic problems which are not solved so far. Live observations and taxonomic methods adapted to the extreme chemical matrix are necessary for correct identification.     

Morphology,Phylogeny, and Diversity of Trichonympha (Parabasalia: Hypermastigida) of the Wood‐Feeding Cockroach Cryptocercus punctulatus

ABSTRACT. Trichonympha is one of the most complex and visually striking of the hypermastigote parabasalids—a group of anaerobic flagellates found exclusively in hindguts of lower termites and the wood‐feeding cockroach Cryptocercus—but it is one of only two genera common to both groups of insects. We investigated Trichonympha of Cryptocercus using light and electron microscopy (scanning and transmission), as well as molecular phylogeny, to gain a better understanding of its morphology, diversity, and evolution. Microscopy reveals numerous new features, such as previously undetected bacterial surface symbionts, adhesion of post‐rostral flagella, and a distinctive frilled operculum. We also sequenced small subunit rRNA gene from manually isolated species, and carried out an environmental polymerase chain reaction (PCR) survey of Trichonympha diversity, all of which strongly supports monophyly of Trichonympha from Cryptocercus to the exclusion of those sampled from termites. Bayesian and distance methods support a relationship between Trichonympha species from termites and Cryptocercus, although likelihood analysis allies the latter with Eucomonymphidae. A monophyletic Trichonympha is of great interest because recent evidence supports a sister relationship between Cryptocercus and termites, suggesting Trichonympha predates the Cryptocercus‐termite divergence. The monophyly of symbiotic bacteria of Trichonympha raises the intriguing possibility of three‐way co‐speciation among bacteria, Trichonympha, and insect hosts.     

Termite-Microbe Symbiotic System and Its Efficient Degradation of Lignocellulose

Termites thrive in the tropics and play an important role in lignocellulose degradation. This ability depends mainly on intestine microbes in the gut, but most of them are so-called unculturable microbes, which can not be cultivated by traditional culture methods. The recent development of molecular approaches such as the PCR method has made it possible to access the enormous numbers of unculturable microbes in the gut of termites.

This review explains our research on the ecological role of the termite, the termite-microbe symbiotic system, and the functions of lignocellulose degradation using various molecular methods. In the future, new technologies such as genomics should make it possible to analyze and utilize unculturable microbial resources in natural environments.     

Screening of Optimal Cellulases from Symbiotic Protists of Termites through Expression in the Secretory Pathway of Saccharomyces cerevisiae

For direct and efficient ethanol production from cellulosic materials, we screened optimal cellulases from symbiotic protists of termites through heterologous expression with Saccharomyces cerevisiae. 11 cellulases, belonging to glycoside hydrolase families 5, 7, and 45 endoglucanases (EGs), were confirmed to produce with S. cerevisiae for the first time. A recombinant yeast expressing SM2042B24 EG I was more efficient at degrading carboxylmethyl cellulose than was Trichoderma reesei EG I, a major EG with high cellulolytic activity.     

Field observations of intercolony aggression and territory changes inHeterotermes aureus (Isoptera: Rhinotermitidae)

Intercolony aggression was observed for a southwestern desert subterranean termite, Heterotermes aureus(Snyder), in bait plots in a Sonoran Desert grassland in Arizona. Intermittent conflict took place at the sites of corrugatedpaper rolls on the boundary between two colonies. Rows of dead termites locked in combat were found within the corrugations, with additional dead termites usually in the soil beneath the roll. Dead soldiers constituted 64 to 100% of termites recovered from sites of intercolony conflict. Ongoing intercolony aggression is likely involved in the maintenance of discrete H. aureusterritories.     

Damage and ecological characteristics of termite Neotermes koshunensis on Taiwan cherry tree Cerasus campanulata in Okinawa Island

Termites are typical house pests that can also be harmful pests for living trees, although this topic has not received much attention. To clarify the damage to trees caused by dry-wood termites (Neotermes koshunensis), and the ecological characteristics of such damage, we conducted a study on Taiwan cherry trees (Cerasus campanulata) grown in parks, historical sites, and streets in the central-southern area of Okinawa Island, a subtropical region. Damage by N. koshunensis was confirmed in 21 of the 36 sites surveyed (58.3%) and in 76 of the 1076 trees surveyed (7.1%). However, damage by Formosan subterranean termites (Coptotermes formosanus), a house pest, was only observed at six sites (16.7%), and 10 trees (0.9%), indicating that most damage was caused by N. koshunensis. Furthermore, the probability of the presence of damaged trees close to other damaged trees was significantly higher than the probability of the presence of damaged trees close to undamaged trees, implying that destructive colonies spread from damaged trees to other trees nearby. Therefore, care for trees in the initial stages of termite invasion seems to be the best method for preventing the spread N. koshunensis damage to other trees in the same area. To our knowledge, this study is the first to report that dry-wood termite N. koshunensis are harmful pests for Taiwan cherry trees in Okinawa Island. Our results could be used to establish dry-wood termite countermeasures for garden tree species.     

白蚁消化系统转化和降解木质纤维素酶研究进展

木质纤维素是地球上最丰富的有机聚合物,白蚁是古老但进化最成功的高效木质纤维素降解者之一.了解白蚁降解高度抗性植物聚合物的机制对工业上生物质能源转化和生物仿生设计有重要的借鉴和指导价值.白蚁和其共生微生物产生的木质纤维素酶在其转化利用木质纤维素上发挥着重要作用.本文从来源作用方面对白蚁自身及其肠道原虫、细菌和真菌产生的纤...     

白蚁及共生微生物木质纤维素水解酶的种类

白蚁是热带生态系统重要的木质纤维素降解者。白蚁种类丰富,可分成高等白蚁和低等白蚁,食性也具有各自特点。白蚁自身可以产生纤维素酶,主要是GHF9的内切葡聚糖酶(EG),也有β-葡萄糖苷酶(GB)。低等白蚁共生的原虫中已发现丰富的纤维素酶基因,属于GHF5,7和45。同时还有其他相关功能基因,如木聚糖酶和果胶类物质水解酶。高等白蚁肠道中没有共生原虫。高等培菌白蚁可以利用共生蚁巢伞属真菌促进木质纤维素降解,真菌可以产生纤维素酶,果胶质水解酶类、木聚糖酶,同时还产生可能与木质素分解相关的一种漆酶,但是从分子水平,关于共生真菌纤维素水解酶的研究还较少。白蚁肠道已分离出许多具有木质纤维素降解能力的菌株,最近的研究也发现了大量细菌纤维素酶基因。白蚁-共生系统丰富的木质纤维素水解酶类为发展生物方法开发纤维素乙醇这一思路提供有价值的资源。     

白蚁肠道共生微生物的作用:酵母,一个“隐身”的特别菌群

长期以来,白蚁对木质纤维素的降解能力令人惊叹,毫无疑问,其在全球碳循环中扮演着一个十分重要的角色。这一强大功能的实现极大地依赖于一种特别的肠道\"消化液(digestome)\",它的构成不仅包括了来自白蚁自身产生的木质纤维素降解酶系统,还来源于独特与多样的肠道共生微生物的贡献(包括了古细菌、细菌、酵母以及其他真核生物),它们的协同作用能有效地将木质纤维素生物质高效转化为乙酸、甲烷、二氧化碳、氢气等物质。然而,到目前为止,我们对这类昆虫的独特肠道生物转化系统的认识还很不深入,特别是针对肠道内的那些各类共生微生物菌群的功能、白蚁与共生微生物间的相互关系、以及潜在的科学与应用价值还无法给予明确的科学解释,更不用说针对其肠道中的共生酵母菌群,一类通常被忽略的独特微生物。近20多年来,越来越多的研究证据表明,白蚁肠道共生酵母在与寄主的关系中表现了不可或缺的重要性与独特功能,已被证明广泛分布于不同白蚁及许多其他昆虫的肠道中。随着近20年来越来越多昆虫肠道共生微生物酵母群被发现和鉴定,他们潜在的功能以及与寄主的共生机制被逐步解析,这些研究结果进一步揭示了\"隐身\"的昆虫肠道酵母类微生物菌群与寄主的营养、关键生物质转化过程中的重要酶系统、转化过程中的关键中间产物的转化与利用、抵御外源性的重要病原物,甚至对白蚁种群繁衍的远缘交配等方面均可能发挥了重要和不可缺少的作用。本文将试图归纳相关研究的最新进展,系统总结与解析白蚁肠道来源共生酵母的重要科学价值及其在不同领域的潜在应用前景。     

白蚁-共生微生物系统降解木质纤维素研究进展

开发利用木质纤维素材料能显著增加地球上可再生资源的储备量.白蚁分布广泛,常见于热带和亚热带地区,它们借助细菌、古细菌、真菌等肠道微生物和原生动物协同降解食物中的木质纤维素,在生态系统的碳、氮循环中发挥着十分重要的作用.本文概括了近年来白蚁肠道微生物研究的进展,特别是近年来已被证明的肠道微生物在木质纤维素降解方面的作用,...     

Why are so many trees hollow?

In many living trees, much of the interior of the trunk can be rotten or even hollowed out. Previously, this has been suggested to be adaptive, with microbial or animal consumption of interior wood producing a rain of nutrients to the soil beneath the tree that allows recycling of those nutrients into new growth via the trees roots. Here I propose an alternative (non-exclusive) explanation: such loss of wood comes at very little cost to the tree and so investment in costly chemical defence of this wood is not economic. I discuss how this theory can be tested empirically.     

Hydrogen emission by three wood-feeding subterranean termite species (Isoptera: Rhinotermitidae): Production and characteristics

Abstract Hydrogen emission by wood-feeding termites, Coptotermes formosanus, Reticulitermes flavipes and Reticulitermes virginicus, was investigated upon a cellulosic substrate as their food source. The emission rates among the three species tested were significantly different and R. virginicus demonstrated the greatest H₂ emission at 4.78 ± 0.15 μmol/h/g body weight. In a sealed test apparatus, H₂ emission for each termite species showed a quick increase at the initial incubation hours (3–6 h), followed by a slower growth, possibly due to the feedback inhibition by gas accumulation. Further investigation revealed that continuous H₂ emission could be maintained by reducing the H₂ partial pressure in the sealed container. The bioconversion of cellulose to molecular H₂ by the subterranean termites tested could reach as high as 3 858 ± 294 μmol/g cellulose, suggesting that the termite gut system is unique and efficient in H₂ conversion from cellulosic substrate.     

The challenge of biomimetic design for carbon-neutral buildings using termite engineering

Abstract The main aim of this paper is to present humanity and termites as design partners in the creation of a new dimension of ecosystem understanding. The paper by Turner and Soar, “Beyond biomimicry: What termites can tell us about realizing the living building” (2008) opens up a new era in how we think of human habitations, not only on earth, but perhaps on other planets, and using the termite model as the corner stone of innovative engineering. We know that termites are masters of constructing ‘buildings’ that meet all nutrition, energy, waste disposal needs, shelter, and food sources for many other animals and insects. We need to emulate the symbiotic abilities of termites to survive over time, for we all live on this symbiotic planet, and symbiosis is natural and common.     

近25年台湾乳白蚁生物学研究进展

台湾乳白蚁Coptotermes formosanus是广泛分布于全球亚热带和温带地区的食木害虫,主要危害各种木质结构和林木。由于台湾乳白蚁造成的巨大经济损失和破坏,近年来受到学界高度关注。深入了解台湾乳白蚁生物学是防治的基础,本文系统综述了2000年以来发表的相关论文。台湾乳白蚁的全球分布是由东亚多次引进和桥头堡效应共同造成的,随着全球气候的变化,预计其适宜分布范围还将不断增加。由于台湾乳白蚁的觅食、挖掘和交哺等行为与其化学防治（饵剂法和化学屏障法）紧密相关,得到了较为深入的研究。近年来,一系列具有踪迹、聚集、挖掘和诱食活性的信息化合物被成功鉴定和筛选,也为诱杀台湾乳白蚁提供了新的思路和方向。由于台湾乳白蚁对病原微生物具有免疫应答和行为抗性,其生物防治的研究一度陷入僵局,但RNA干扰等技术能够抑制台湾乳白蚁的抗病机制,有望在不久的未来开发出新的防治技术。此外,台湾乳白蚁也与木腐菌、蓝变真菌和木霉菌等环境微生物,以及原生鞭毛虫、细菌、古细菌和病毒等肠道微生物具有复杂的相互作用。台湾乳白蚁具有两个独立但互补的纤维素降解系统,一个是由自身产生的纤维素酶构成的内源纤维素降解系统,另一个是由后肠的共生微生物构成的外源性纤维素降解系统,其高效降解木质纤维素的能力对生物质能研究具有重要的启发意义。     

Localized treatments using commercial dust and liquid formulations of fipronil against Coptotermes formosanus （Isoptera： Rhinotermitidae） in the laboratory

Use of proper application methods and formulations of termiticides are im- portant to reduce their negative impact to the environment. In this study, we conducted laboratory experiments to determine the effect of localized treatments with commercial dust and liquid formulations of fipronil against Formosan subterranean termites, Coptoter- mes formosanus Shiraki. The test arena consisted of a specially designed 16-chambered structure with a center chamber connected to 5 foraging chambers that themselves were connected to 10 additional foraging chambers. One peripheral chamber received a liquid or dust treatment and termites were released in the center chamber. Results showed that 〉 91% of the termites were dead within the 9-d test period despite the localized treatment of only 1 foraging chamber. Termites that were still alive after 9 d were transferred to an untreated dish and held for 10 more days. The majority of those termites were dead and the rest were moribund on day 19. Regardless of the specific dish treated, both formulations of fipronil were found to be highly efficacious. Termites did not exhibit repellency to either formulation. Our results suggest that localized （or spot） treatment with either commer- cially available dust or liquid formulations of fipronil can be a viable option for control of a termite infestation where complete soil drenching is not desirable.