Heterogeneous space-division multiplexing and joint wavelength switching demonstration

We demonstrate a six spatial-mode, wavelength-routing network interoperable with few-mode, coupled-multi-core, and single-mode fiber spans using a custom 57-port wavelength-selective switch configured for joint-switching of spatial-superchannels

Temperate infection in a virus–host system previously known for virulent dynamics

The blooming cosmopolitan coccolithophore Emiliania huxleyi and its viruses (EhVs) are a model for density-dependent virulent dynamics. EhVs commonly exhibit rapid viral reproduction and drive host death in high-density laboratory cultures and mesocosms that simulate blooms. Here we show that this system exhibits physiology-dependent temperate dynamics at environmentally relevant E. huxleyi host densities rather than virulent dynamics, with viruses switching from a long-term non-lethal temperate phase in healthy hosts to a lethal lytic stage as host cells become physiologically stressed. Using this system as a model for temperate infection dynamics, we present a template to diagnose temperate infection in other virus–host systems by integrating experimental, theoretical, and environmental approaches. Finding temperate dynamics in such an established virulent host–virus model system indicates that temperateness may be more pervasive than previously considered, and that the role of viruses in bloom formation and decline may be governed by host physiology rather than by host–virus densities

Seasonal Mixed Layer Depth Shapes Phytoplankton Physiology, Viral Production, and Accumulation In the North Atlantic

Seasonal shifts in phytoplankton accumulation and loss largely follow changes in mixed layer depth, but the impact of mixed layer depth on cell physiology remains unexplored. Here, we investigate the physiological state of phytoplankton populations associated with distinct bloom phases and mixing regimes in the North Atlantic. Stratification and deep mixing alter community physiology and viral production, effectively shaping accumulation rates. Communities in relatively deep, early-spring mixed layers are characterized by low levels of stress and high accumulation rates, while those in the recently shallowed mixed layers in late-spring have high levels of oxidative stress. Prolonged stratification into early autumn manifests in negative accumulation rates, along with pronounced signatures of compromised membranes, death-related protease activity, virus production, nutrient drawdown, and lipid markers indicative of nutrient stress. Positive accumulation renews during mixed layer deepening with transition into winter, concomitant with enhanced nutrient supply and lessened viral pressure

Seasonal mixed layer depth shapes phytoplankton physiology, viral production, and accumulation in the North Atlantic

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Diaz, B. P., Knowles, B., Johns, C. T., Laber, C. P., Bondoc, K. G. V., Haramaty, L., Natale, F., Harvey, E. L., Kramer, S. J., Bolaños, L. M., Lowenstein, D. P., Fredricks, H. F., Graff, J., Westberry, T. K., Mojica, K. D. A., Haëntjens, N., Baetge, N., Gaube, P., Boss, E., Carlson, C. A., Behrenfeld, M. J., Van Mooy, B. A. S., Bidle, K. D. Seasonal mixed layer depth shapes phytoplankton physiology, viral production, and accumulation in the North Atlantic. Nature Communications, 12(1), (2021): 6634, https://doi.org/10.1038/s41467-021-26836-1.Seasonal shifts in phytoplankton accumulation and loss largely follow changes in mixed layer depth, but the impact of mixed layer depth on cell physiology remains unexplored. Here, we investigate the physiological state of phytoplankton populations associated with distinct bloom phases and mixing regimes in the North Atlantic. Stratification and deep mixing alter community physiology and viral production, effectively shaping accumulation rates. Communities in relatively deep, early-spring mixed layers are characterized by low levels of stress and high accumulation rates, while those in the recently shallowed mixed layers in late-spring have high levels of oxidative stress. Prolonged stratification into early autumn manifests in negative accumulation rates, along with pronounced signatures of compromised membranes, death-related protease activity, virus production, nutrient drawdown, and lipid markers indicative of nutrient stress. Positive accumulation renews during mixed layer deepening with transition into winter, concomitant with enhanced nutrient supply and lessened viral pressure.This work was made possible by NASA’s Earth Science Program in support of the North Atlantic Aerosol and Marine Ecosystem Study (15-RRNES15-0011 and 0NSSC18K1563 to K.D.B.; NNX15AF30G to M.J.B.), as well as with support from the National Science Foundation (OIA-2021032 to K.D.B., OCE-157943 to C.A.C., and OCE-1756254 to B.A.S.V.M.), the Gordon and Betty Moore Foundation (Award# 3789 to K.G.V.B.), and NASA’s Future Investigators in Space Science and Technology program (FINESST; grant #826380 to K.D.B.; graduate support to BD)

Absolutely Sound Testing of Lifted Codes

In this work we present a strong analysis of the testability of a broad, and to date the most interesting known, class of “affine-invariant ” codes. Affine-invariant codes are codes whose coordinates are associated with a vector space and are invariant under affine transformations of the coordinate space. Affine-invariant linear codes form a natural abstraction of algebraic properties such as linearity and low-degree, which have been of significant interest in theoretical computer science in the past. The study of affine-invariance is motivated in part by its relationship to property testing: Affine-invariant linear codes tend to be locally testable under fairly minimal and almost necessary conditions. Recent works by Ben-Sasson et al. (CCC 2011) and Guo et al. (ITCS 2013) have introduced a new class of affine-invariant linear codes based on an operation called “lifting”. Given a base code over a t-dimensional space, its m-dimensional lift consists of all words whose restriction to every t-dimensional affine subspace is a codeword of the base code. Lifting not only captures the most familiar codes, which can be expressed as lifts of low-degree polynomials, it also yields new codes when lifting “medium-degree ” polynomials whose rate is better than that of corresponding polynomial codes, and all other combinatorial qualities are no worse. In this work we show that codes derived from lifting are also testable in an “absolutely sound” way. Specifically, we consider the natural test: Pick a random affine subspace of base dimension and verify that a given word is a codeword of the base code when restricted to the chosen subspace. We show that this test accepts codewords with probability one, while rejecting words at constant distance from the code with constant probability (depending only on the alphabet size). This work thus extends the results of Bhattacharyya et al. (FOCS 2010) and Haramaty et al. (FOCS 2011), while giving concrete new codes of higher rate that have absolutely sound testers.

Apoptosis and the selective survival of host animals following thermal bleaching in zooxanthellate corals

During the past several decades, numerous reports from disparate geographical areas have documented an increased frequency of “bleaching” in reef-forming corals. The phenomenon, triggered by increased sea surface temperatures, occurs when the cnidarian hosts digest and/or expel their intracellular, photosynthetic dinoflagellate symbionts (“zooxanthellae” in the genus Symbiodinium). Although coral bleaching is often followed by the death of the animal hosts, in some cases, the animal survives and can be repopulated with viable zooxanthellae. The physiological factors determining the ability of the coral to survive bleaching events are poorly understood. In this study, we experimentally established that bleaching and death of the host animal involve a caspase-mediated apoptotic cascade induced by reactive oxygen species produced primarily by the algal symbionts. In addition, we demonstrate that, although some corals naturally suppress caspase activity and significantly reduce caspase concentration under high temperatures as a mechanism to prevent colony death from apoptosis, even sensitive corals can be prevented from dying by application of exogenous inhibitors of caspases. Our results indicate that variability in response to thermal stress in corals is determined by a four-element, combinatorial genetic matrix intrinsic to the specific symbiotic association. Based on our experimental data, we present a working model in which the phenotypic expression of this symbiont/host relationship places a selective pressure on the symbiotic association. The model predicts the survival of the host animals in which the caspase-mediated apoptotic cascade is down-regulated

Temperate infection in a virus-host system previously known for virulent dynamics.

The blooming cosmopolitan coccolithophore Emiliania huxleyi and its viruses (EhVs) are a model for density-dependent virulent dynamics. EhVs commonly exhibit rapid viral reproduction and drive host death in high-density laboratory cultures and mesocosms that simulate blooms. Here we show that this system exhibits physiology-dependent temperate dynamics at environmentally relevant E. huxleyi host densities rather than virulent dynamics, with viruses switching from a long-term non-lethal temperate phase in healthy hosts to a lethal lytic stage as host cells become physiologically stressed. Using this system as a model for temperate infection dynamics, we present a template to diagnose temperate infection in other virus-host systems by integrating experimental, theoretical, and environmental approaches. Finding temperate dynamics in such an established virulent host-virus model system indicates that temperateness may be more pervasive than previously considered, and that the role of viruses in bloom formation and decline may be governed by host physiology rather than by host-virus densities