Symbiosis of a termite and a sclerotium-forming fungus: Sclerotia mimic termite eggs

Brown balls, of a similar size but different shape to termite eggs, were found frequently in the piles of eggs of the subterranean termite Reticulitermes speratus. rDNA analysis identified the ball as the sclerotia of the fungus, Fibularhizoctonia sp. nov, which is phylogenetically closest to decay fungi, Athelia spp. Laboratory observation showed that the workers gathered the eggs and the sclerotia indiscriminately, even if they were widely scattered in a Petri dish, and piled them up in a specific place for egg care. We compared the morphology of the eggs with that of sclerotia of Fibularhizoctonia spp. and Athelia spp. in relation to egg carrying behaviour, and found that the workers could only carry the Fibularhizoctonia spp. sclerotia whose diameters were similar to the short diameter of the eggs. We also conducted a bioassay using termite eggs and dummy eggs (glass beads and sea sand) of two diameter-classes, coated with or without the egg-derived chemicals. The workers recognized the eggs based on a combination of the size, shape, and chemical cues. All the results suggested that the sclerotia mimic the eggs both morphologically and chemically. Finally, we found that the workers suppressed germination of sclerotia, and termite egg survival increased in the presence of sclerotia only if they were tended by the workers. If the workers were removed experimentally, the sclerotia germinated and grew by exploiting termite eggs. These results suggest that the sclerotia protect termite eggs from putative pathogens.     

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.     

Detection and quantitation of iron in ferritin,transferrin and labile iron pool (LIP) in cardiomyocytes using 55Fe and storage phosphorimaging

Dysregulated iron metabolism has a detrimental effect on cardiac function. The importance of iron homeostasis in cardiac health and disease warrants detailed studies of cardiomyocyte iron uptake, utilization and recycling at the molecular level. In this study, we have performed metabolic labeling of primary cultures of neonatal rat cardiomyocytes with radioactive iron coupled with separation of labeled iron-containing molecules by native electrophoresis followed by detection and quantification of incorporated radioiron by storage phosphorimaging. For the radiolabeling we used a safe and convenient beta emitter ⁵⁵Fe which enabled sensitive and simultaneous detection and quantitation of iron in cardiomyocyte ferritin, transferrin and the labile iron pool (LIP). The LIP is believed to represent potentially dangerous redox–active iron bound to uncharacterized molecules. Using size-exclusion chromatography spin micro columns, we demonstrate that iron in the LIP is bound to high molecular weight molecule(s) (≥5000?Da) in the neonatal cardiomyocytes.     

Phylogenetic Placement of Trichonympha

Flagellated protists of the Class Hypermastigida have previously been classified on morphology alone, since no molecular sequences have been available. We have isolated DNA from 350 cells of the hypermastigote Trichonympha , manually collected from the hindgut of Zootermopsis angusticollis , and used this DNA as template for polymerase chain reaction amplification of the small-subunit ribosomal RNA gene. The DNA sequence of the amplified fragment is closely related to that of a previously-unidentified gut symbiont from the termite Reticulitermes flavipes , and phylogenetic analysis places both sequences as a sister group to the known trichomonads. in agreement with the morphological classification.