Microbiomes are ubiquitous and are found in the ocean, the soil, and in/on other living organisms. Changes in the microbiome can impact the health of the environmental niche in which they reside. In order to learn more about these communities, different approaches based on data from multiple omics have been pursued. Metagenomics produces a taxonomical profile of the sample, metatranscriptomics helps us to obtain a functional profile, and metabolomics completes the picture by determining which byproducts are being released into the environment. Although each approach provides valuable information separately, we show that, when combined, they paint a more comprehensive picture. We conclude with a review of network-based approaches as applied to integrative studies, which we believe holds the key to in-depth understanding of microbiomes.

Myosin light chain kinase (MLCK)-dependent phosphorylation of the regulatory light chain (RLC) of cardiac myosin is known to play a beneficial role in heart disease, but the idea of a phosphorylation-mediated reversal of a hypertrophic cardiomyopathy (HCM) phenotype is novel. Our previous studies on transgenic (Tg) HCM-RLC mice revealed that the D166V (Aspartate166 →Valine) mutation-induced changes in heart morphology and function coincided with largely reduced RLC phosphorylation in situ. We hypothesized that the introduction of a constitutively phosphorylated Serine15 (S15D) into the hearts of D166V mice would prevent the development of a deleterious HCM phenotype. In support of this notion, MLCK-induced phosphorylation of D166V-mutated hearts was found to rescue some of their abnormal contractile properties. Tg-S15D-D166V mice were generated with the human cardiac RLC-S15D-D166V construct substituted for mouse cardiac RLC and were subjected to functional, structural, and morphological assessments. The results were compared with Tg-WT and Tg-D166V mice expressing the human ventricular RLC-WT or its D166V mutant, respectively. Echocardiography and invasive hemodynamic studies demonstrated significant improvements of intact heart function in S15D-D166V mice compared with D166V, with the systolic and diastolic indices reaching those monitored in WT mice. A largely reduced maximal tension and abnormally high myofilament Ca 2+ sensitivity observed in D166V-mutated hearts were reversed in S15D-D166V mice. Lowangle X-ray diffraction study revealed that altered myofilament structures present in HCM-D166V mice were mitigated in S15D-D166V rescue mice. Our collective results suggest that expression of pseudophosphorylated RLC in the hearts of HCM mice is sufficient to prevent the development of the pathological HCM phenotype.cardiomyopathy | hemodynamics | myocardial contraction | X-ray structure | myosin RLC

The myosin essential light chain (ELC) is a structural component of the actomyosin cross-bridge, but its function is poorly understood, especially the role of the cardiac specific N-terminal extension in modulating actomyosin interaction. Here, we generated transgenic (Tg) mice expressing the A57G (alanine to glycine) mutation in the cardiac ELC known to cause familial hypertrophic cardiomyopathy (FHC). The function of the ELC N-terminal extension was investigated with the Tg-Δ43 mouse model, whose myocardium expresses a truncated ELC. Low-angle X-ray diffraction studies on papillary muscle fibers in rigor revealed a decreased interfilament spacing (≈ 1.5 nm) and no alterations in cross-bridge mass distribution in Tg-A57G mice compared to Tg-WT, expressing the full-length nonmutated ELC. The truncation mutation showed a 1.3-fold increase in I(1,1)/I(1,0), indicating a shift of cross-bridge mass from the thick filament backbone toward the thin filaments. Mechanical studies demonstrated increased stiffness in Tg-A57G muscle fibers compared to Tg-WT or Tg-Δ43. The equilibrium constant for the cross-bridge force generation step was smallest in Tg-Δ43. These results support an important role for the N-terminal ELC extension in prepositioning the cross-bridge for optimal force production. Subtle changes in the ELC sequence were sufficient to alter cross-bridge properties and lead to pathological phenotypes.

No abstract

Apalachicola Bay, a bar-built, sub-tropical estuary in the northeastern Gulf of Mexico (GOM), USA, receives freshwater from the Apalachicola River and exchanges water with the GOM at 4 sltes. The output from a 3-dimensional circulation model and nitrogen measurements in the river and the estuary over a 2 yr period were used to determine nitrogen input to the estuary and exchange with the GOM. The Apalachicola River was the major nitrogen source to the estuary and accounted for 92 and 73% of the total dissolved Inorganic and organic mtrogen (DIN and DON) input, respectively Nitrogen input from the GOM provided the remainder. DIN compnsed 61 % of total dissolved nitrogen (TDN) input to the estuary from the river and 26% of TDN input from the GOM. Maxima in TDN input to the estuary occurred during the high river-flow period (October to February). In contrast, TDN input minima occurred d u r~n g the summer (May to September), when river flow was low. Benthic ammonium flux to the water column was maxinlum durlng the summer. However, it was not large enough to satisfy phytoplankton nitrogen demand during that period. The fractlon of DIN input that was exported to the GOM increased linearly as estuarine water residence time decreased from 2 wk during summer to less than 3 d during winter. Seasonal nitrogen budgets indicated that DIN export to the GOM was maximum during winter (87 + 5.4 mg N m-' d-') and minimum during summer (9 + 1.4 mg N d-'). In contrast to the large decrease in DIN export to the GOM between these 2 periods, DON export to the GOM decreased from 81 * 5.8 mg N m-2 d-' during winter to only 45 i 3.2 mg N m-2 d-' during summer. Estimated denitrification rates indicated that 9% of the annual total nitrogen input to the estuary was removed by that mechanism. The f ratio in Apalachlcola Bay varied from 0.1 1 during the summer to 0.74 during the winter and averaged 0.19 for a 2 yr period. On an annual basis, DON ~n p u t to the estuary and export to the GOM were in balance, while 66% of DIN input to the estuary was exported to the GOM. The nitrogen budget for Apalachicola Bay was balanced to within 6 % of total nitrogen input.