Ayayee Paul A, Larsen Thomas, Sabree Zakee
Department of Evolution, Ecology and Organismal Biology, Ohio State University , USA.
Laboratory for Radiometric Dating and Stable Isotope Research, Christian-Albrechts-Universität Kiel , Kiel , Germany.
PeerJ. 2016 May 18;4:e2046. doi: 10.7717/peerj.2046. eCollection 2016.
Insect gut microbes have been shown to provide nutrients such as essential amino acids (EAAs) to their hosts. How this symbiotic nutrient provisioning tracks with the host's demand is not well understood. In this study, we investigated microbial essential amino acid (EAA) provisioning in omnivorous American cockroaches (Periplaneta americana), fed low-quality (LQD) and comparatively higher-quality dog food (DF) diets using carbon stable isotope ratios of EAAs (δ (13)CEAA). We assessed non-dietary EAA input, quantified as isotopic offsets (Δ(13)C) between cockroach (δ (13)CCockroach EAA) and dietary (δ (13)CDietary EAA) EAAs, and subsequently determined biosynthetic origins of non-dietary EAAs in cockroaches using (13)C-fingerprinting with dietary and representative bacterial and fungal δ (13)CEAA. Investigation of biosynthetic origins of de novo non-dietary EAAs indicated bacterial origins of EAA in cockroach appendage samples, and a mixture of fungal and bacterial EAA origins in gut filtrate samples for both LQD and DF-fed groups. We attribute the bacteria-derived EAAs in cockroach appendages to provisioning by the fat body residing obligate endosymbiont, Blattabacterium and gut-residing bacteria. The mixed signatures of gut filtrate samples are attributed to the presence of unassimilated dietary, as well as gut microbial (bacterial and fungal) EAAs. This study highlights the potential impacts of dietary quality on symbiotic EAA provisioning and the need for further studies investigating the interplay between host EAA demands, host dietary quality and symbiotic EAA provisioning in response to dietary sufficiency or deficiency.
昆虫肠道微生物已被证明能为宿主提供必需氨基酸等营养物质。这种共生营养供应如何与宿主需求相匹配，目前尚不清楚。在本研究中，我们利用必需氨基酸的碳稳定同位素比率（δ(13)C EAA），研究了杂食性美国蟑螂（美洲大蠊）在食用低质量（LQD）和相对高质量狗粮（DF）日粮时微生物必需氨基酸（EAA）的供应情况。我们评估了非日粮EAA的输入，以蟑螂（δ(13)C蟑螂EAA）和日粮（δ(13)C日粮EAA）EAA之间的同位素偏移（Δ(13)C）来量化，随后使用日粮以及代表性细菌和真菌的δ(13)C EAA进行(13)C指纹分析，确定蟑螂中非日粮EAA的生物合成来源。对新生非日粮EAA生物合成来源的研究表明，蟑螂附肢样本中的EAA来源于细菌，而LQD和DF喂养组的肠道滤液样本中EAA的来源是真菌和细菌的混合物。我们将蟑螂附肢中细菌衍生的EAA归因于常驻脂肪体的专性内共生菌Blattabacterium和肠道细菌的供应。肠道滤液样本的混合特征归因于未同化的日粮以及肠道微生物（细菌和真菌）EAA的存在。本研究强调了日粮质量对共生EAA供应的潜在影响，以及进一步研究宿主EAA需求、宿主日粮质量和共生EAA供应之间相互作用以应对日粮充足或不足的必要性。
