Ministry of Agriculture Key Laboratory of Molecular Biology of Crop Pathogens and Insects, Institute of Insect Sciences, Zhejiang University, Hangzhou, Zhejiang, PR China.
J Insect Physiol. 2012 Oct;58(10):1368-75. doi: 10.1016/j.jinsphys.2012.07.012. Epub 2012 Jul 31.
The physicochemical conditions in an insect's gut microenvironment have been reported to play an important role in food processing and metabolisms. In this study, the profiles of oxygen, pH, redox potentials, and hydrogen in the isolated guts of the fungus-growing termite, Odontotermes formosanus Shiraki, were investigated with a microeletrode system. Compared with those in other termites, O. formosanus exhibited a relatively lower oxygen partial pressures in its gut system ranging from 0 to 8.6 kPa. The pH profile in the different gut compartments was neutral (pH 6.1-7.4) except in the rectum region. The average redox potentials at the center of each gut region (except rectum) were high and ranged from approximately +70 to +310 mV. Especially, as the central intermediate during lignocellulose degradation, hydrogen partial pressures in the hindgut paunch lumen were recorded as high as 10.4 kPa. Furthermore, thirteen metal ion concentrations in the termite's gut system, nest symbiotic fungal combs, as well as the nest soil samples were evaluated with Inductively Coupled Plasma Mass Spectrometry (ICP-MS), which indicated that six metal ions (K, Mg, Mn, Ba, Se, and Mo) out of 13 ions recorded in the major digestive tract regions show some significant differences in their spatial distributions. A significant enrichment of some metal ions was also observed in the rectum, fungal combs, and the nest soil samples. The lower oxygen profiles, neutral pH, higher redox potentials, and higher hydrogen accumulation with the characterized spatial distributions for metal ions in the digestive tract of O. formosanus, highlighted the most important distinctiveness of the fungus-growing termites in its gut microenvironments, suggesting that the unique structure and functions of the intestinal ecosystem may present within its gut.
昆虫肠道微环境的物理化学条件被报道在食物加工和新陈代谢中发挥重要作用。在这项研究中，使用微电极系统研究了真菌培养白蚁 Odontotermes formosanus Shiraki 离体肠道中的氧、pH 值、氧化还原电位和氢的分布。与其他白蚁相比，O. formosanus 的肠道系统中的氧分压相对较低，范围为 0 到 8.6 kPa。不同肠道区域的 pH 值分布呈中性（pH 6.1-7.4），除了直肠区域。每个肠道区域中心的平均氧化还原电位较高，范围约为+70 到+310 mV。特别是，作为木质纤维素降解过程中的中间产物，后肠嗉囊腔中的氢分压记录高达 10.4 kPa。此外，使用电感耦合等离子体质谱法（ICP-MS）评估了白蚁肠道系统、巢共生真菌梳以及巢土壤样本中的 13 种金属离子浓度，结果表明，在主要消化道区域记录的 13 种离子中，有 6 种金属离子（K、Mg、Mn、Ba、Se 和 Mo）在空间分布上存在显著差异。在直肠、真菌梳和巢土壤样本中也观察到一些金属离子的显著富集。O. formosanus 肠道中氧分压较低、pH 值中性、氧化还原电位较高、氢积累量较高，并且金属离子具有特征性的空间分布，这突出了真菌培养白蚁在肠道微环境中的最重要特征，表明肠道内可能存在独特的肠道生态系统结构和功能。
