Biodegradation of polyalcohol ethoxylate by a wastewater microbial consortium

Polyalcohol ethoxylate (PAE), an anionic surfactant, is the primary component in most laundry and dish wash detergents and is therefore highly loaded in domestic wastewater. Its biodegradation results in the formation of several metabolites and the fate of these metabolites through wastewater treatment plants, graywater recycling processes, and in the environment must be clearly understood. Biodegradation pathways for PAE were investigated in this project with a municipal wastewater microbial consortium. A microtiter-based oxygen sensor system was utilized to determine the preferential use of potential biodegradation products. Results show that while polyethylene glycols (PEGs) were readily degraded by PAE acclimated microorganisms, most of the carboxylic acids tested were not degraded. Biodegradation of PEGs suggests that hydrophobe–hydrophile scission was the dominant pathway for PAE biodegradation in this wastewater community. Ethylene glycol (EG) and diethylene glycol (DEG) were not utilized by microbial populations capable of degrading higher molecular weight EGs. It is possible that EG and DEG may accumulate. The microtiter-based oxygen sensor system was successfully utilized to elucidate information on PAE biodegradation pathways and could be applied to study biodegradation pathways for other important contaminants.     

The early years--across the bench from Bruce (1963-1966)

This personal reflection on the author's experience as Bruce Merrifield's first graduate student has been adapted from a talk given at the Merrifield Memorial Symposium at the Rockefeller University on November 13, 2006.     

Back to the future: ribonuclease A

Pancreatic ribonuclease A (EC 3.1.27.5, RNase) is, perhaps, the best-studied enzyme of the 20th century. It was isolated by René Dubos, crystallized by Moses Kunitz, sequenced by Stanford Moore and William Stein, and synthesized in the laboratory of Bruce Merrifield, all at the Rockefeller Institute/University. It has proven to be an excellent model system for many different types of experiments, both as an enzyme and as a well-characterized protein for biophysical studies. Of major significance was the demonstration by Chris Anfinsen at NIH that the primary sequence of RNase encoded the three-dimensional structure of the enzyme. Many other prominent protein chemists/enzymologists have utilized RNase as a dominant theme in their research. In this review, the history of RNase and its offspring, RNase S (S-protein/S-peptide), will be considered, especially the work in the Merrifield group, as a preface to preliminary data and proposed experiments addressing topics of current interest. These include entropy-enthalpy compensation, entropy of ligand binding, the impact of protein modification on thermal stability, and the role of protein dynamics in enzyme action. In continuing to use RNase as a prototypical enzyme, we stand on the shoulders of the giants of protein chemistry to survey the future.     

Role of Endothelial Cell Ion Channels in the Resistance Artery Function

Endothelium-dependent hyperpolarizing factor (EDHF) underlies nitric oxide and prostacyclin-independent arterial relaxation. As the influence of EDHF increases with decreasing artery size, it plays an important role in vascular regulation. Initially suggested to represent a diffusible factor, EDHF is now thought to represent a variable input in different arteries from a factor(s) and the spread of hyperpolarizing current from the endothelium to the smooth muscle. Key to unravelling this pathway has been the demonstration that hyperpolarization within the endothelium can be blocked using a combination of the K_Ca channel blockers, apamin and charibdotoxin. As a consequence, the relaxation of vascular smooth muscle, which represents the end point of the EDHF pathway, is blocked. This review discusses the evidence that a differential distribution of ion channels between the smooth muscle and endothelial cells underlies the EDHF pathway. Also, that a diffusible factor, which may well be K ions released by the endothelium, acts alongside the spread of hyperpolarization through myoendothelial gap junctions to explain EDHF-evoked smooth muscle relaxation. While the relative importance of each of these two components can vary between arteries, together they can explain the EDHF phenomenon.     

Comparative locomotor performance of marsupial and placental mammals

Marsupials are often considered inferior to placental mammals in a number of physiological characters. Because locomotor performance is presumed to be an important component of fitness, we compared marsupials and placentals with regard to both maximal running speeds and maximal aerobic speeds (=speed at which the maximal rate of oxygen consumption, VOlmax, is attained). Maximal aerobic speed is related to an animal's maximal sustainable speed, and hence is a useful comparative index of stamina.
Maximal running speeds of 11 species of Australian marsupials, eight species of Australian murid rodents, two species of American didelphid marsupials, and two species of American rodents were measured in the laboratory and compared with data compiled from the literature. Our values are greater than, or equivalent to, those reported previously. Marsupials and placentals do not differ in maximal running speeds (nor do Australian rodents differ from non-Australian rodents). Within these groups, however, species and families may differ considerably. Some of the interspecific variation in maximal running speeds is related to differences in habitat: species inhabiting open habitats (e.g. deserts) tend to be faster than are species from habitats with more cover, or arboreal species.
Maximal aerobic speeds (compiled from the literature) were higher in large species than in small species. However, marsupials and placentals show no general difference with regard to maximal aerobic speeds.
Maximal running speeds and maximal aerobic speeds for 18 species of mammals were not correlated, after correcting for correlations with body size. Thus, the fastest sprinters do not necessarily have high maximal aerobic speeds.