Chinook and Coho salmon hybrids linked to habitat and climatic changes on Vancouver Island,British Columbia

Between 2013 and 2019, 63 presumed Chinook salmon Oncorhynchus tshawytscha sampled primarily in the Strait of Georgia (0.63% of total sample) were identified as potential Chinook–Coho (Oncorhynchus kisutch) hybrids by the presence of anomalous microsatellite genotypes. Their hybrid origin was confirmed by single nucleotide polymorphism amplification of two species‐specific amplicons. Mitochondrial DNA indicated that most of these fish resulted from the hybridization of Coho salmon females and Chinook salmon males. Although no diagnostic external features were identified, several individuals displayed an abnormal scale arrangement on the caudal peduncle. One hybrid juvenile examined for meristics exhibited a pyloric caeca count intermediate between published values for Chinook and Coho salmon. Most hybrids originated in the Cowichan River during the 2014 brood year. Their prevalence in the watershed is a naturally occurring event, likely exacerbated by prolonged low water levels which limit habitat and delay Chinook salmon spawning, in addition to the differential abundance of the parental species. This research is the first to document ongoing natural hybridization (Chinook–Coho salmon crosses) and link it to habitat and climatic changes, and includes the identification of eight F1 adults and two juvenile backcross or F2 hybrids. The potential negative impacts of hybridization, particularly in Coho salmon through potential introgression, warrant hybrid identification as an ecosystem monitoring tool within a survey program.     

Degradation of triglycerides by a pseudomonad isolated from milk: the roles of lipase and esterase studied using recombinant strains over-producing, or specifically deficient in these enzymes

The roles of lipase and esterase in causing hydrolytic spoilage of milk by a highly lipolytic psychrotrophic strain of Pseudomonas fluorescens , LS107d2, has been studied. Strains of LS107d2 have been constructed that over-produce, or are specifically deficient in, a lipase (encoded by lip A ) and an esterase (encoded by est A ). Southern blot analysis reveals that LS107d2 contains only one esterase and one lipase (encoded by est A and lip A ) and this was confirmed by the phenotypes of mutants on triolein and tributyrin-containing agar. Analysis of broth cultures showed that the lipase is secreted into the culture medium; in contrast, the esterase is not secreted. Free fatty acid (FFA) levels in whole milk cultures of wild-type, over-producing and the mutant strains of LS107d2 have been examined. From these studies it is concluded that esterase is not involved in the accumulation of FFA by hydrolysing short chain fatty acid esters; that the highly lipolytic phenotype of LS107d2 is due solely to a single secreted lipase; and that the main FFA accumulated in milk cultures of LS107d2 are C4, C16, C18 and C18: 1. Evidence is also presented demonstrating that FFA degradation, as well as production, determines the level of FFA in milk contaminated with lipolytic organisms.     

Deoxynucleoside-sensitive mutants of Salmonella typhimurium

Summary Thymineless mutants ofSalmonella typhimurium which are able to grow with low added concentrations of thymine (20 M) fall into two classes on the basis of growth on deoxyribose as sole carbon source. Those which can grow are deoxyribomutase negative and those which cannot are deoxyriboaldolase negative. The former class are inhibited by deoxynucleosides and this provides a method for discriminating between different classes oftlr mutants ofEscherichia coli K12, which cannot utilize deoxyribose as a carbon source. It is suggested that the sensitivity of deoxyriboaldolase negative strains is due to the accumulation of deoxyribose-5-phosphate. The data also indicate that deoxyribose-5-phosphate is the inducer of thymidine phosphorylase. It seems that one or both of the deoxyribose phosphates is the toxic compound, and that reversal of inhibition by ribonucleosides is due to inhibition of the enzymes catalysing their formation from deoxynucleosides. We propose that the symbolsdrm anddra be used to denote the structural genes for deoxyribomutase and deoxyriboaldolase respectively.     

A genetic analysis of early development in pink (Oncorhynchus gorbuscha) and chum salmon (Oncorhynchus keta) at three different temperatures

A factorial mating design was employed in which five males were mated to each of five females in each of two stocks for both pink and chum salmon. The resulting embryos and alevins were incubated at constant water temperatures of 4, 8, and 16 degrees C for pink salmon and 3, 8, and 15 degrees C for chum salmon. Variation among families in alevin and fry survival rates, hatching, button-up time, length, and weight was the least at 8 degrees C. Heritability of traits directly correlated with fitness, such as survival rates and button-up time, was low at all temperatures (h2 less than or equal to 0.25). Maternal effects could account for a substantial portion of the variation in alevin and fry size characters. Nonadditive genetic variance accounted for more of the variation in fry size characters than in those of alevins. Negative genetic correlations were observed between embryo survival and subsequent alevin size and between hatching time and subsequent alevin and fry size. Genotype-temperature interactions could underlie a substantial amount of phenotypic variation in the developmental characters examined for both species.     

Enzyme secretion in E. coli K12 : studies on alkaline phosphatase synthesis using an unsaturated fatty-acid auxotroph.

The role of unsaturated fatty-acid starvation, and of the substitution of $\text{trans}$ for $\text{cis}$ fatty acids in the membrane phospholipid, on the secretion of alkaline phosphatase, has been investigated. A system in which alkaline phosphatase synthesis was initiated by a temperature shift has been used to obviate possible complications resulting from phosphate depletion. In contrast to earlier reports, we find (a) there is very little effect of unsaturated fatty-acid starvation on the synthesis of alkaline phosphatase; (b) the synthesis of both β-galactosidase and alkaline phosphatase synthesis was severely reduced below 27–30°C in cells grown on $\text{trans}\text{Δ}{}^9$ 16:1 fatty-acid, compared to cells grown on the $\text{cis}\text{Δ}{}^9$ 16:1 analogue. Thus no $\text{preferential}$ effect on alkaline phosphatase synthesis was observed.     

Disease-causing Mutations in the Cystic Fibrosis Transmembrane Conductance Regulator Determine the Functional Responses of Alveolar Macrophages

Alveolar macrophages (AMs) play a major role in host defense against microbial infections in the lung. To perform this function, these cells must ingest and destroy pathogens, generally in phagosomes, as well as secrete a number of products that signal other immune cells to respond. Recently, we demonstrated that murine alveolar macrophages employ the cystic fibrosis transmembrane conductance regulator (CFTR) Cl⁻ channel as a determinant in lysosomal acidification (Di, A., Brown, M. E., Deriy, L. V., Li, C., Szeto, F. L., Chen, Y., Huang, P., Tong, J., Naren, A. P., Bindokas, V., Palfrey, H. C., and Nelson, D. J. (2006) Nat. Cell Biol. 8, 933–944). Lysosomes and phagosomes in murine cftr^−/− AMs failed to acidify, and the cells were deficient in bacterial killing compared with wild type controls. Cystic fibrosis is caused by mutations in CFTR and is characterized by chronic lung infections. The information about relationships between the CFTR genotype and the disease phenotype is scarce both on the organismal and cellular level. The most common disease-causing mutation, ΔF508, is found in 70% of patients with cystic fibrosis. The mutant protein fails to fold properly and is targeted for proteosomal degradation. G551D, the second most common mutation, causes loss of function of the protein at the plasma membrane. In this study, we have investigated the impact of CFTR ΔF508 and G551D on a set of core intracellular functions, including organellar acidification, granule secretion, and microbicidal activity in the AM. Utilizing primary AMs from wild type, cftr^−/−, as well as mutant mice, we show a tight correlation between CFTR genotype and levels of lysosomal acidification, bacterial killing, and agonist-induced secretory responses, all of which would be expected to contribute to a significant impact on microbial clearance in the lung.