Seasonal Variation in the Structure of a Marine Benthic Microbial Community

Abstract The patterns of seasonal variation in the structure of a marine benthic microbial community were examined using phospholipid fatty acid analysis (PLFA). Principal component analysis of PLFA profiles indicated a strong seasonal pattern dominated the variance within the data set. Three functional groups of microorganisms (phototrophic microeukaryotes, and two groups of anaerobic bacteria) were disproportionately abundant in the communities that mapped to either extreme of the first principle component. Phototrophic microeukaryotes were most abundant and exhibited the greatest relative abundance during periods of cold water. In contrast, the two functional groups of anaerobic bacteria showed the greatest relative abundance during times of warm water. Differential responses by these groups, and macrofaunal deposit feeders, to light intensity and water temperature were offered as the proximal causes of the observed patterns. Received: 28 April 1997; Accepted: 10 September 1997     

A novel sterol peroxide from the sea anenome Metridium senile

Nine 5 alpha, 8 alpha-epidioxy delta 6 and delta 6,9(11) sterols were identified including the hitherto unknown (22E)-5,8-epidioxy-5 alpha, 8 alpha-stigmasta-6,9(11),22-trien-3 beta-ol 9 from the sea anenome Metridium senile based on 200 MHz 1Hnmr and mass spectral data.     

Response of Heterotrophic Planktonic Bacteria to the Zebra Mussel Invasion of the Tidal Freshwater Hudson River

Abstract Invasions of aquatic ecosystems by exotic bivalves are known to cause dramatic changes in phytoplankton and some other groups, but their effect on the microbial component is unknown. The invasion of the tidal freshwater Hudson River by the exotic zebra mussel (Dreissena polymorpha) has caused large changes in several components of the Hudson's food web. Planktonic bacteria in the tidal freshwater Hudson are a major part of the food web, and mediate important processes in the carbon budget. We used a long-term data set, spanning four years prior to the zebra mussel (ZM) invasion and four years post-invasion, to describe ZM effects on planktonic bacteria. Small and meso-scale experiments were conducted to specifically examine direct consumption of bacteria by ZM, as well as effects on protozoans. Bacterial abundances in the Hudson have increased roughly 2× since the ZM arrived, making it clear that direct consumption by Dreissena is a minor process. Experiments show that ZM do not remove bacteria from Hudson River water, but are very effective at clearing flagellated protozoans, the major predator of bacteria. The observed changes in bacterial abundance have not been accompanied by equally large changes in bacterial productivity, suggesting growth is primarily limited by carbon supply. Bacterial production has not declined despite a dramatic decline of phytoplankton, confirming previous suggestions that bacteria and phytoplankton are not strongly linked in the Hudson. As a result of the increase in bacterial abundance and removal of phytoplankton, the absolute and relative contributions of bacterial carbon to living particulate organic carbon (POC) standing stocks have increased dramatically. The maintenance of the bacterial component of the Hudson River's food web may be one mechanism whereby consumers are ``insulated' from effects of zebra mussel consumption of phytoplankton carbon. Received: 24 October 1997; Accepted: 9 February 1998     

Deletion of DNA lying close to the glkA locus induces ectopic sporulation in Streptomyces coelicolor A3(2)

Streptomyces coelicolor A3(2) J1668 sporulated ectopically in the substrate hyphae (the Esp phenotype) with the same time course as sporulation in the aerial hyphae. Examination of related strains implied that the Esp phenotype was caused by the deletion of DNA that lies close to, but is distinct from, the glucose kinase gene ( glkA ). Co-transduction of the Esp phenotype with the deletion present in J1668 confirmed this hypothesis. The size of the deletion was found to be 7.4 kb. Construction of a strain carrying both the J1668 deletion and a whiG mutation demonstrated that the Esp phenotype depends on at least one of the genes required for the differentiation of aerial hyphae into spores.     

Exploring the utility of Deep Red Anthraquinone 5 for digital staining of ex vivo confocal micrographs of optically sectioned skin

We investigated the utility of the fluorescent dye Deep Red Anthraquinone 5 (DRAQ5) for digital staining of optically sectioned skin in comparison to acridine orange (AO). Eight fresh-frozen thawed Mohs discard tissue specimens were stained with AO and DRAQ5, and imaged using an ex vivo confocal microscope at three wavelengths (488 nm and 638 nm for fluorescence, 785 nm for reflectance). Images were overlaid (AO + Reflectance, DRAQ5 + Reflectance), digitally stained, and evaluated by three investigators for perceived image quality (PIQ) and histopathological feature identification. In addition to nuclear staining, AO seemed to stain dermal fibers in a subset of cases in digitally stained images, while DRAQ5 staining was more specific to nuclei. Blinded evaluation showed substantial agreement, favoring DRAQ5 for PIQ (82%, Cl 75%-90%, Gwet's AC 0.74) and for visualization of histopathological features in (81%, Cl 73%-89%, Gwet's AC 0.67), supporting its use in digital staining of multimodal confocal micrographs of skin.