Growth of “Seeded” Cellulolytic Enrichment Cultures on Mesquite Wood

Eleven enrichment cultures were developed by a “seeded” enrichment culture technique, and one was developed by a simple enrichment technique. The seeded enrichment, the pure “seed,” and the simple enrichment cultures were compared during growth on mesquite wood, cotton, carboxymethylcellulose, and cellobiose. All of the enrichment cultures were cellulolytic and exceeded the pure seed cultures in mesquite wood hydrolysis and/or viable cell count. Yeast extract improved, but was not essential for, growth of the seeded enrichment cultures on carboxymethylcellulose. Two of the seeded enrichment cultures, CAD5 and CAD11, grew best at 37°C and pH 7.0 on mesquite wood. A 1.0% (wt/vol) wood concentration was optimum for their growth.     

Pyruvate metabolism after in vivo exposure to oral arsenic

This study investigated altered pyruvate metabolism after prolonged oral arsenic exposure. Male rats were given access to deionized drinking water containing 0, 40 or 85 ppm sodium arsenate (As⁵⁺) for 3 weeks. Respiration studies with mitochondria isolated from treated animals indicated decreased state 3 respiration (with ADP) and decreased respiratory control ratios (RCR) for pyruvate/malate-mediated respiration, but not for succinate-mediated respiration, as compared to control respiration values. In addition, pyruvate dehydrogenase activity was measured, in both liver and intestine, before and after Mg-activation in vitro. After 3 weeks, the effects of arsenic at the highest dose level were pronounced on the basal pyruvate dehydrogenase activity (before activation) as well as the total pyruvate dehydrogenase (after activation). The inhibition of pyruvate dehydrogenase activity both before and after Mg-activation suggests an arsenic effect on mitochondrial pyruvate metabolism which, in part, involves inhibition of pyruvate decarboxylase. Evidence is also presented which may indicate an arsenic effect on the kinase and/or phosphatase which regulate pyruvate dehydrogenase activity.     

The immune response of allophenic mice to the synthetic polymer GLΦ

The immune response of allophenic mice of type C57BL/6(A × SJL) F₁ to GL administered in complete Freund's adjuvant was tested. Control mice of the three strains C57BL/6, A, and SJL are all nonresponders to this antigen. However, the F₁ generations of C57BL/6 × A, C57BL/6 × SJL, and A × SJL were all responders to the antigen, so that the complementarity of at least two genes is confirmed. The allophenic mice showed no further complementation beyond the F₁ generation, a result which may argue against the possibility that more than two genes control the response to GL in these mouse strains. Characterization of the allophenic mice over several months showed that they exhibit chimeric drift, both in their coat color and in peripheral white blood cell population. There is no apparent correlation of coat color to the lymphocyte composition of the mice at any one time. The mice are true chimeras, since killing of the two populations of white blood cells with two different anti-H-2 sera produced a 100 percent killing. The immune response of individual allophenic mice to GL showed a good correlation to the number of A × SJL lympho-cytes in the animal.Abbreviations used in this paper are GL an amino acid polymer of 57 %l-glutamic acid, 38%l-lysine, and 5%l-phenylalanine - GLT¹⁵ an amino acid polymer ofl-glutamic acid,l-lysine, and 15 %l-tyrosine - (T,G)-A-L an amino acid polymer having a polylysine backbone with side chains of polyd-l-alanine, terminating in short sequences of tyrosine and glutamic acid - GAT₁₀ an amino acid polymer of 60%l-glutamic acid, 30%l-alanine, and 10%l-tyrosine - GLA₅ an amino acid polymer of 57%l-glutamic acid, 38%l-lysine, and 5%l-alanine - DNP 2,4 dinitrophenyl - BGG bovine gamma globulin - FCS fetal calf serum - PWBC peripheral white blood cell - SWBC spleen white blood cell - T cell thymus-derived lymphocyte - B cell bone marrow-derived lymphocyte     

LAS inhibition of diffusion and uptake of tritiated uridine during teleost embryogenesis

Synopsis Fathead minnow embryos (Pimephales promelas Rafinesque) of 5 different developmental ages (5, 33, 48, 72 and 96 hrs after fertilization) were used as controls and exposed for 2 hrs to a solution of 0.25 Ci ml^–1 of³H-Uridine. Another set of embryos (5, 33, 48, 72 and 96 hrs after fertilization) were subjected to the same treatment except that during the one hour immediately preceding the³H-Uridine incubation, the control embryos were placed in water while the experimental embryos were placed in water containing 15 ppm 11.2 LAS. In both cases, radiation counts minute^–1 embryo^–1 and per milligram of embryo increased over the 4 day developmental period. The embryos with LAS treatment displayed lower radiation counts at all ages as compared to controls, indicating an inhibition of diffusion and uptake of³H-Uridine and/or RNA synthesis. The possible mechanism of LAS is discussed.     

Potential Pathogens in the Environment: Cultural Reactions and Nucleic Acid Studies on Klebsiella pneumoniae from Clinical and Environmental Sources

The phenotypic and nucleic acid properties of Klebsiella pneumoniae have been studied on cultures obtained from six different habitats (humans, vegetables, seeds, trees, rivers, and pulp mills). The 19 cultural reactions of 107 isolates varied significantly only in tryptophanase activity and dulcitol fermentation. The percentage of guanine plus cytosine base composition of 41 isolates varied from 53.9 to 59.2%. The range of percentage of guanine plus cytosine base composition for environmental klebsiellas was broader than that for the cultures of human origin. The range of deoxyribonucleic acid relative reassociation (homology) to the human K. pneumoniae reference strain extended from 5% to 100% and the chromosome molecular weights ranged from 2,200 × 10⁶ to 3,000 × 10⁶. The species of K. pneumoniae is thus molecularly more heterogeneous than previously thought and most isolates of human, pulp mill, and river origin are genetically indistinguishable. The presence of K. pneumoniae therefore represents a deterioration of the microbiological quality of the environment and should be considered of public health significance. At the present time the health significance of the molecularly more divergent strains, primarily of vegetable and seed origin, their relationship to klebsiellas of human origin, or to other genera of the Enterobacteriaceae is unclear.     

Isolation and Genetic Analysis of Mutant Strains of CHLAMYDOMONAS REINHARDI Defective in Gametic Differentiation

Impotent mutant strains of Chlamydomonas reinhardi, mating-type (mt) plus, are described that have normal growth and motility but fail to differentiate into normal gametes. Procedures for their isolation and their genetic analysis are described. Five of the imp strains (imp-2, imp-5, imp-l, imp-7, and imp-8) exhibit no flagellar agglutination when mixed with mt- or mt+ gametes and the mutations are shown to be unlinked to the mt locus (with the possible exception of imp-7). Two of the strains (imp-3 and imp-4) carry leaky mutations that affect cell fusion; neither mutation is found by tetrad analysis to be linked to mt or to the other. Cells of the imp-1 strain agglutinate well with mt- gametes and active agglutination continues for up to 48 hours, but cell fusion occurs only very rarely. Analysis of these rare zygotes indicates that imp-1 is closely linked to the mt+ locus, and fine-structural studies reveal that imp-1 gametes produce a mutant mating structure involved in zygotic cell fusion. The development of sexuality in C. reinhardi therefore appears amenable to genetic dissection.     

Spatiotemporal spread of Plasmodium falciparum mutations for resistance to sulfadoxine-pyrimethamine across Africa, 1990–2020

BackgroundSulfadoxine-pyrimethamine (SP) is recommended in Africa in several antimalarial preventive regimens including Intermittent Preventive Treatment in pregnant women (IPTp), Intermittent Preventive Treatment in infants (IPTi) and Seasonal Malaria Chemoprevention (SMC). The effectiveness of SP-based preventive treatments are threatened in areas where Plasmodium falciparum resistance to SP is high. The prevalence of mutations in the dihydropteroate synthase gene (pfdhps) can be used to monitor SP effectiveness. IPTi-SP is recommended only in areas where the prevalence of the pfdhps540E mutation is below 50%. It has also been suggested that IPTp-SP does not have a protective effect in areas where the pfdhps581G mutation, exceeds 10%. However, pfdhps mutation prevalence data in Africa are extremely heterogenous and scattered, with data completely missing from many areas.Methods and findingsThe WWARN SP Molecular Surveyor database was designed to summarize dihydrofolate reductase (pfdhfr) and pfdhps gene mutation prevalence data. In this paper, pfdhps mutation prevalence data was used to generate continuous spatiotemporal surface maps of the estimated prevalence of the SP resistance markers pfdhps437G, pfdhps540E, and pfdhps581G in Africa from 1990 to 2020 using a geostatistical model, with a Bayesian inference framework to estimate uncertainty. The maps of estimated prevalence show an expansion of the pfdhps437G mutations across the entire continent over the last three decades. The pfdhps540E mutation emerged from limited foci in East Africa to currently exceeding 50% estimated prevalence in most of East and South East Africa. pfdhps540E distribution is expanding at low or moderate prevalence in central Africa and a predicted focus in West Africa. Although the pfdhps581G mutation spread from one focus in East Africa in 2000, to exceeding 10% estimated prevalence in several foci in 2010, the predicted distribution of the marker did not expand in 2020, however our analysis indicated high uncertainty in areas where pfdhps581G is present. Uncertainty was higher in spatial regions where the prevalence of a marker is intermediate or where prevalence is changing over time.ConclusionsThe WWARN SP Molecular Surveyor database and a set of continuous spatiotemporal surface maps were built to provide users with standardized, current information on resistance marker distribution and prevalence estimates. According to the maps, the high prevalence of pfdhps540E mutation was to date restricted to East and South East Africa, which is reassuring for continued use of IPTi and SMC in West Africa, but continuous monitoring is needed as the pfdhps540E distribution is expanding. Several foci where pfdhps581G prevalence exceeded 10% were identified. More data on the pfdhps581G distribution in these areas needs to be collected to guide IPTp-SP recommendations. Prevalence and uncertainty maps can be utilized together to strategically identify sites where increased surveillance can be most informative. This study combines a molecular marker database and predictive modelling to highlight areas of concern, which can be used to support decisions in public health, highlight knowledge gaps in certain regions, and guide future research.