The Linux command line: a complete introduction

You've experienced the shiny, point-and-click surface of your Linux computer—now dive below and explore its depths with the power of the command line. The Linux Command Line takes you from your very first terminal keystrokes to writing full programs in Bash, the most popular Linux shell. Along the way you'll learn the timeless skills handed down by generations of gray-bearded, mouse-shunning gurus: file navigation, environment configuration, command chaining, pattern matching with regular expressions, and more

COLUMNARIS DISEASE OF FISHES

Columnaris disease is an acute to chronic bacterial infection that affects anadromous salmonids and virtually all species of warmwater fishes. Davis (1922), who first described the disease, named it columnaris because the causal bacterial cells seen in wet mounts of affected gills and fins were arranged in columnar aggregations. Ordal and Rucker (1944) were the first to isolate the causal organism and, based on cellular morphology, identified it as a myxobacterium. Organisms classified in the order Myxobacterales are long, thin gram-negative rods that are motile on agar media by a creeping or flexing motion. They have a life cycle composed of vegetative cells, microcysts (resting cells), and fruiting bodies, or only vegetative cells and microcysts. Ordal and Rucker (1944) reported that the myxobacterium from columnaris disease produced both fruiting bodies and microcysts and named the organism Chondrococcus columnaris. Garnjobst (1945) studied strains of the columnaris bacterium and reported that microcysts were present but not fruiting bodies. Because fruiting bodies could not be demonstrated, she placed the organism in the genus Cytophaga and suggested Cytophaga columnaris. However, in the eighth edition of Bergey\u27s Manual of Determinative Bacteriology (Buchanan and Gibbons 1974), it was stated that the columnaris bacterium produced neither fruiting bodies nor microcysts. Therefore it was removed from the Myxobacterales, placed in the order Cytophagales, and renamed Flexibacter columnaris

Medium for isolation of Yersinia enterocolitica

A new differential plate medium, CAL (cellobiose-arginine-lysine) agar, was developed and evaluated for the isolation of Yersinia enterocolitica. For all but two isolates tested, distinctive colonies were formed on CAL agar within 40 h of incubation at 25 degrees C. These colonies were readily recognized and isolated from a mixed inoculum containing 10 other bacteria commonly found in water and fecal specimens. Y. enterocolitica was presumptively identified based on colonial morphology from 9 of 10 fecal cultures containing the organism when inoculated to CAL agar and incubated for 40 h at 25 degrees C. No false-positive identification were made. The medium has been shown to be as sensitive as MacConkey agar in supporting growth of Y. enterocolitica, and it can be used in broth from for enumeration of the organism from water and liquid specimens. The medium is easily made and does not need to be autoclaved.</jats:p

Stability of antibiotics under growth conditions for thermophilic anaerobes

It was shown that the inhibitory effect of kanamycin and streptomycin in a growing culture of Clostridium thermohydrosulfuricum JW 102 is of limited duration. To screen a large number of antibiotics, their stability during incubation under the growth conditions of thermophilic clostridia was determined at 72 and 50 degrees C by using a 0.2% yeast extract-amended prereduced mineral medium with a pH of 7.3 or 5.0. Half-lives were determined in a modified MIC test with Escherichia coli, Staphylococcus aureus, and Bacillus megaterium as indicator strains. All compounds tested were similar at the two temperatures or more stable at 50 than at 72 degrees C. The half-life (t1/2) at pH 7.3 and 72 degrees C ranged from 3.3 h (k = 7.26 day-1, where k [degradation constant] = 1/t1/2) for ampicillin to no detectable loss of activity for kanamycin, neomycin, and other antibiotics. Apparently some compounds (e.g., lasalocid and neomycin) became more potent during incubation (k greater than 0). A change to pH 5.0 caused some compounds to become more labile (e.g., kanamycin) and others (e.g., streptomycin) to become more stable than at pH 7.3.</jats:p