Source and Fate of Lipids in Polar Gelatinous Zooplankton

The presence or absence of accumulated lipids in arctic and Antarctic medusae and ctenophores was determined by visual examination of living specimens with a dissecting microscope. Lipid accumulations were obvious because of their high refractive indices. Lipids were seen in many of the 200+ gelatinous zooplankton specimens collected. They always consisted of various-sized droplets and larger masses within the lumen of the gastrovascular system. No true depot lipids or adipose tissue were present. The accumulation of lipids was observed in feeding animals, suggesting that the prey-derived lipids were unmodified. Disappearance of lipids in starved animals suggested that lipids are taken up and assimilated. In medusae, they occurred in the stomach, ring and/or radial canals. In most ctenophores, lipids were found in the meridional canals below the comb rows. However, in one ctenophore species, Mertensia ovum, lipids are stored in special sacs associated with the tentacle bulbs. Lipids were more frequently observed in arctic than in Antarctic gelatinous zooplankton. A review of the literature suggests that in the Antarctic, the average lipid content of gelatinous predators is about 3% DW (range = 0.4-6%), whereas in the Arctic it is nearly three times higher, about 8% DW (range = 1.5-22%). These differences are probably related to the amounts of lipids in their prey. The abundance of lipid-rich Calanus spp. copepods in the Arctic may be responsible for the high levels of lipids in gelatinous predators.Key words: lipids, gelatinous zooplankton, ctenophores, medusae, Arctic, Antarctic, polar, feeding, starvationMots clés: lipides, zooplancton gélatineux, cténaires, méduses, Arctique, Antarctique, polaire, alimentation, état de jeûn

Chemical synergy between ionophore PBT2 and zinc reverses antibiotic resistance

The World Health Organization reports that antibiotic-resistant pathogens represent an imminent global health disaster for the 21st century. Gram-positive superbugs threaten to breach last-line antibiotic treatment, and the pharmaceutical industry antibiotic development pipeline is waning. Here we report the synergy between ionophore-induced physiological stress in Gram-positive bacteria and antibiotic treatment. PBT2 is a safe-for-human-use zinc ionophore that has progressed to phase 2 clinical trials for Alzheimer's and Huntington's disease treatment. In combination with zinc, PBT2 exhibits antibacterial activity and disrupts cellular homeostasis in erythromycin-resistant group A Streptococcus (GAS), methicillin-resistant Staphylococcus aureus (MRSA), and vancomycin-resistant Enterococcus (VRE). We were unable to select for mutants resistant to PBT2-zinc treatment. While ineffective alone against resistant bacteria, several clinically relevant antibiotics act synergistically with PBT2-zinc to enhance killing of these Gram-positive pathogens. These data represent a new paradigm whereby disruption of bacterial metal homeostasis reverses antibiotic-resistant phenotypes in a number of priority human bacterial pathogens.IMPORTANCE The rise of bacterial antibiotic resistance coupled with a reduction in new antibiotic development has placed significant burdens on global health care. Resistant bacterial pathogens such as methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus are leading causes of community- and hospital-acquired infection and present a significant clinical challenge. These pathogens have acquired resistance to broad classes of antimicrobials. Furthermore, Streptococcus pyogenes, a significant disease agent among Indigenous Australians, has now acquired resistance to several antibiotic classes. With a rise in antibiotic resistance and reduction in new antibiotic discovery, it is imperative to investigate alternative therapeutic regimens that complement the use of current antibiotic treatment strategies. As stated by the WHO Director-General, "On current trends, common diseases may become untreatable. Doctors facing patients will have to say, Sorry, there is nothing I can do for you."Lisa Bohlmann, David M. P. De Oliveira, Ibrahim M. El-Deeb, Erin B. Brazel, Nichaela Harbison-Pric

Environmental effects of dredging on sediment nutrients, carbon and granulometry in a tropical estuary

10.1007/s10661-006-9253-2Environmental Monitoring and Assessment1271-31-13EMAS