Effects of Prechilling and Sequential Washing on Enumeration of Microorganisms from Refuse

Techniques were evaluated for formation of a liquid inoculum from shredded municipal refuse, including chilling the refuse at 4°C prior to blending and multiple washing and blending cycles. The average count of cellulolytic bacteria from six different detachment treatments was 5.1 × 10⁴ cells per g (dry weight) of refuse with a range of 0.7 × 10⁴ to 12.7 × 10⁴ cells per g (dry weight). The liquid obtained from blending the refuse in phosphate buffer followed by hand squeezing was the selected detachment procedure. The inoculum formation procedure was validated by the addition of ruminal cellulolytic bacteria to refuse and recovery of the cellulolytic bacteria by most-probable-number enumerations. The ratio of measured to expected cell counts among tests in which different volumes of ruminal fluid were added to refuse ranged from 2.7 to 14.4. There was no evidence of anaerobic cellulolytic fungi in a refuse sample.     

Protein dynamics from chemical shift and dipolar rotational spin-echo 15N NMR

The partial collapse of dipolar and chemical shift tensors for peptide NH and for the amide NH at cross-link sites in cell wall peptidoglycan, of intact lyophilized cells of Aerococcus viridans, indicates NH vector root-mean-square fluctuations of 23 degrees. This result is consistent with the local mobility calculated in typical picosecond regime computer simulations of protein dynamics in the solid state. The experimental root-mean-square angular fluctuations for both types of NH vectors increase to 37 degrees for viable wet cells at 10 degrees C. The similarity in mobilities for both general protein and cell wall peptidoglycan suggests that one additional motion in wet cells involves cooperative fluctuations of segments of cell walls, attached proteins, and associated cytoplasmic proteins.     

Characterization of the cDNA coding for mouse plasminogen and localization of the gene to mouse chromosome 17

A full-length cDNA coding for mouse plasminogen has been isolated and characterized. The cDNA is 2720 bp in length (excluding the poly(A) tail) and contains a 24-bp 5' noncoding region, an open reading frame of 2436 bp, and a 3' noncoding region of 257 bp. The open reading frame codes for 812 amino acids and includes a signal peptide that is likely 19 amino acids in length and the mature protein of 793 amino acids. The calculated Mr of mouse plasminogen is 88,706 excluding carbohydrate. There are two potential N-linked carbohydrate addition sites; one of which is glycosylated in human, bovine, and porcine plasminogens. Mouse plasminogen was found to contain two additional amino acids compared to the human protein. In addition, mouse and human plasminogens were found to be 79 and 76% identical at the protein and DNA levels, respectively. Analysis of the segregation of two allelic forms, Plgb and Plgd, of plasminogen DNA in three sets of recombinant inbred strains has allowed the localization of the mouse plasminogen gene to the proximal end of mouse chromosome 17 within the t complex and close to the locus D17Rp17. The Plg gene is deleted in the semidominant deletion mutant, hair-pintail (Thp).     

Metabolism of glyphosate in Pseudomonas sp. strain LBr

Metabolism of glyphosate (N-phosphonomethylglycine) by Pseudomonas sp. strain LBr, a bacterium isolated from a glyphosate process waste stream, was examined by a combination of solid-state 13C nuclear magnetic resonance experiments and analysis of the phosphonate composition of the growth medium. Pseudomonas sp. strain LBr was capable of eliminating 20 mM glyphosate from the growth medium, an amount approximately 20-fold greater than that reported for any other microorganism to date. The bacterium degraded high levels of glyphosate, primarily by converting it to aminomethylphosphonate, followed by release into the growth medium. Only a small amount of aminomethylphosphonate (about 0.5 to 0.7 mM), which is needed to supply phosphorus for growth, could be metabolized by the microorganism. Solid-state 13C nuclear magnetic resonance analysis of strain LBr grown on 1 mM [2-13C,15N]glyphosate showed that about 5% of the glyphosate was degraded by a separate pathway involving breakdown of glyphosate to glycine, a pathway first observed in Pseudomonas sp. strain PG2982. Thus, Pseudomonas sp. strain LBr appears to possess two distinct routes for glyphosate detoxification.     

Cross-species transmission of Giardia spp.: inoculation of beavers and muskrats with cysts of human, beaver, mouse, and muskrat origin

Giardia cysts isolated from humans, beavers, mice, and muskrats were tested in cross-species transmission experiments for their ability to infect either beavers or muskrats. Giardia cysts, derived from multiple symptomatic human donors and used for inoculation of beavers or muskrats, were shown to be viable by incorporation of fluorogenic dyes, excystation, and their ability to produce infections in the Mongolian gerbil model. Inoculation of beavers with 5 x 10(5) Giardia lamblia cysts resulted in the infection of 75% of the animals (n = 8), as judged by the presence of fecal cysts or intestinal trophozoites at necropsy. The mean prepatent period was 13.1 days. An infective dose experiment, using 5 x 10(1) to 5 x 10(5) viable G. lamblia cysts collected by fluorescence-activated cell sorting, demonstrated that doses of between, less than 50, and less than 500 viable cysts were required to produce infection in beavers. Scanning electron microscopy of beaver small intestine revealed that attachment of G. lamblia trophozoites produced lesions in the microvillous border. Inoculation of muskrats with G. lamblia cysts produced infections when the dose of cysts was equal to or greater than 1.25 x 10(5). The inoculation of beavers with Giardia ondatrae or Giardia muris cysts did not produce any infection; however, the administration to muskrats of Giardia cysts of beaver origin resulted in the infection of 62% of the animals (n = 8), with a prepatent period of 5 days. Our results demonstrated that beavers and muskrats could be infected with Giardia cysts derived from humans, but only by using large numbers of cysts.(ABSTRACT TRUNCATED AT 250 WORDS)