Biology subjects

Clifford, A. M.

Publications and source records attributed to Clifford, A. M..

3 recordsLinked to original sources

bioRxiv2022

The hologenome of Osedax frankpressi reveals the genetic interplay for the symbiotic digestion of vertebrate bone

The marine annelid Osedax has evolved a unique heterotrophic symbiosis that allows it to feed exclusively on sunken bones. Yet, the genetic and physiological principles sustaining this symbiosis are poorly understood. Here we show that Osedax frankpressi has a small, AT-rich genome shaped by extensive gene loss. While the Oceanospirillales endosymbiont of Osedax is enriched in genes for carbohydrate and nitrogen metabolism, O. frankpressi has undergone genetic changes to accommodate bone digestion, including the expansion of matrix metalloproteases, and a loss of pathways to synthesize amino acids that are abundant in collagen. Unlike other symbioses, however, innate immunity genes required to acquire and control the endosymbionts are reduced in O. frankpressi. These findings reveal Osedax has evolved an alternative genomic toolkit to bacterial symbiosis where host-symbiont co-dependence has favoured genome simplicity in the host to exploit the nutritionally unbalanced diet of bones. TeaserGenome reduction and adaptations for collagen digestion underpin the symbiosis of Osedax worms to exploit decaying bones.

genomics↗

bioRxiv2022

An Engineered Nanocomposite Copper Coating with Enhanced Antibacterial Efficacy

Contaminated surfaces are a major source of nosocomial infection. To reduce microbial bioburden and surface-based transmission of infectious disease, the use of antibacterial and self-sanitizing surfaces, such as copper (Cu), is being explored in clinical settings. Cu has long been known to have antimicrobial activity. However, Gram-positive microorganisms, a class that includes pathogens commonly responsible for hospital-acquired infection such as Staphylococcus aureus and Clostridioides difficile, are more resilient to its biocidal effect. Inspired by inherently bactericidal nanostructured surfaces found in nature, we have developed an improved Cu coating, engineered to contain nanoscale surface features and thus increase its antibacterial activity against a broader range of organisms. In addition, we have established a new method for facilitating the rapid and continuous release of biocidal metal ions from the coating, through incorporation of an antibacterial metal salt (ZnCl2) with a lower reduction potential than Cu. Electrophoretic deposition (EPD) was used to fabricate our coatings, which serves as a low-cost and scalable route for modifying existing conductive surfaces with complex shape. By tuning both the surface morphology and chemistry, we were able to create a nanocomposite Cu coating that decreased the microbial bioburden of Gram-positive S.aureus by 94% compared to unmodified Cu. Table of Contents O_FIG_DISPLAY_L [Figure 1] M_FIG_DISPLAY Antimicrobial copper (Cu) products are being deployed in clinical settings to decrease microbial bioburden and prevent surface-based transmission of infectious disease. However, Gram-positive bacteria demonstrate increased resistance to Cus biocidal effects. To improve Cus antibacterial efficacy against Gram-positive bacteria, we have developed a hydrophobic Cu coating with cytotoxic nanotopography that facilitates the rapid and continuous release of biocidal metal ions. C_FIG_DISPLAY

bioengineering↗

bioRxiv2021

Red blood cells protect oxygen transport with adrenergic sodium-proton exchangers in hypoxic and hypercapnic white seabass

White seabass (Atractoscion nobilis) are increasingly experiencing periods of low oxygen (O2; hypoxia) and high carbon dioxide (CO2, hypercapnia) due to climate change and eutrophication of the coastal waters of California. Hemoglobin (Hb) is the principal O2 carrier in the blood and in many teleost fishes Hb-O2 binding is compromised at low pH; however, the red blood cells (RBC) of some species regulate intracellular pH with adrenergically-stimulated sodium-proton-exchangers ({beta}-NHE). We hypothesized that RBC {beta}-NHEs in white seabass are an important mechanism that can protect the blood O2-carrying capacity during hypoxia and hypercapnia. We determined the O2-binding characteristics of white seabass blood, the response of RBCs to adrenergic stimulation, and quantified the protective effect of {beta}-NHE activity on Hb-O2 saturation. White seabass had typical teleost Hb characteristics, with a moderate O2 affinity (PO2 at half-saturation; P50 2.9 kPa) that was highly pH-sensitive (Bohr coefficient -0.92; Root effect 52%). The presence of RBC {beta}-NHEs was confirmed by functional, molecular and bioinformatic data and super-resolution imaging revealed, for the first time, the subcellular location of {beta}-NHE protein in vesicle-like structures and on the RBC membrane, and its translocation after adrenergic stimulation. The activation of RBC {beta}-NHEs increased Hb-O2 saturation by [~]8% in normoxia at 1 kPa PCO2, and by up to 20% in hypoxia. Our results confirm that RBC {beta}-NHE activity in white seabass has great potential to protect arterial O2 transport in environmentally relevant conditions of hypoxia and hypercapnia, but also reveal a potential vulnerability of fish to combinations of these stressors.

physiology↗