Biofilm formation in Streptococcus pneumoniae

Biofilm‐grown bacteria are refractory to antimicrobial agents and show an increased capacity to evade the host immune system. In recent years, studies have begun on biofilm formation by Streptococcus pneumoniae, an important human pathogen, using a variety of in vitro model systems. The bacterial cells in these biofilms are held together by an extracellular matrix composed of DNA, proteins and, possibly, polysaccharide(s). Although neither the precise nature of these proteins nor the composition of the putative polysaccharide(s) is clear, it is known that choline‐binding proteins are required for successful biofilm formation. Further, many genes appear to be involved, although the role of each appears to vary when biofilms are produced in batch or continuous culture. Prophylactic and therapeutic measures need to be developed to fight S. pneumoniae biofilm formation. However, much care needs to be taken when choosing strains for such studies because different S. pneumoniae isolates can show remarkable genomic differences. Multispecies and in vivo biofilm models must also be developed to provide a more complete understanding of biofilm formation and maintenance.     

Lessons,narratives, and research directions for a sustainable circular economy

The current enthusiasm for the circular economy (CE) offers a unique opportunity to advance the impact of research on sustainability transitions. Diverse interpretations of CE by scholars, however, produce partly opposing assessments of its potential benefits, which can hinder progress. Here, we synthesize policy-relevant lessons and research directions for a sustainable CE and identify three narratives—optimist, reformist, and skeptical—that underpin the ambiguity in CE assessments. Based on 54 key CE scholars’ insights, we identify three research needs: the articulation and discussion of ontologically distinct CE narratives; bridging of technical, managerial, socio-economic, environmental, and political CE perspectives; and critical assessment of opportunities and limits of CE science–policy interactions. Our findings offer practical guidance for scholars to engage reflexively with the rapid expansion of CE knowledge, identify and pursue high-impact research directions, and communicate more effectively with practitioners and policymakers.     

A Pascal microcomputer program for prediction of protein secondary structure and hydropathic segments

This paper describes a simple Pascal microcomputer program forprediction of protein secondary structure according to the Chouand Fasman algorithm. In addition, it performs an analysis ofthe hydropathic character of the residues for prediction ofexternal/internal regions of the polypeptide chain. Also itsearches for probable glycosylation and phosphorylation sites. Received on July 26, 1985; accepted on May 6, 1986     

Ethanol utilization for metabolite production by Candida utilis strains in liquid medium

Ethanol has been reported to be a gaseous pollutant, originating from the agricultural industry. Interest in its biodegradation has increased over the last two decades. Most of the current studies have focused on its elimination by mixed cultures. This study is part of a broader project intended to utilize Candida utilis strains for gaseous ethanol elimination and to eventually bioconvert them into biomass and/or volatile metabolites. We present here the study of six strains (one from the ATCC and five from the ICIDCA collection) cultivated in a liquid medium, with initial ethanol concentrations of 16 g/l and 32 g/l. At 16 g/l, a maximum ethanol elimination rate of 0.13 g/l × h was obtained in four of the six strains (ATCC 9950, L/375–1, L/375–5 and L/375–10). This rate increased to 0.21 g/l × h with an initial ethanol concentration of 32 g/l. The L/375–5 strain was the best biomass producer (3.3 g/l) at 32 g/l, while the highest ethyl acetate production (0.80 g/l) was obtained with the L/375–1 strain. The L/375–25 and L/375–26 strains which showed very low ethyl acetate production were, by way of contrast, efficient acetaldehyde producers, with 0.54 g/l and 0.66 g/l measured in the broth. While biomass production reached its maximum after two days of culture, the production of acetic acid and ethyl acetate continued during the third day. The results for biomass and metabolite production obtained with the ICIDCA collection strains (L/375–1, L/375–5 and L/375–10) were better than those obtained with the ATCC 9950 strain, although the latter often has been reported to be particularly suitable for metabolite production.     

The production of labeled betaine by incubation of osmolyte-freePseudomonas aeruginosa with radioactive choline

A simple, efficient, and economical method is presented for the preparation of radioactive betaine. It involves the incubation of radioactive choline with osmolyte-freePseudomonas aeruginosa previously grown in hyperosmolar medium with choline as an osmoprotectant. The summarized procedure was as follows: (i) bacteria were grown in high P_i basal salt medium (HP_i-BSM) with 20mm succinate, 18.7mm NH₄Cl, 0.8m NaCl, and 1mm nonradioactive choline. After the bacterial pellet was obtained, it was suspended in deionized water to release osmolytes accumulated during growth; (ii) suspension of the pellet, free of osmolytes, in hyperosmolar HP_i-BSM with [methyl-¹⁴C]-choline (55 nCi/nmol) without the carbon and nitrogen sources. Incubation of the mixture at 37°C for 8–30 h. When only 10% of the initial radioactivity remained in the supernatant, it was withdrawn after centrifugation and the pellet suspended in deionized water. This step released the accumulated betaine plus some contaminants. Purification of betaine contained in the aqueous supernatant was carried out after rotoevaporation to dryness and solubilization of the residue in methanol. The methanolic extract was rotoevaporated to dryness, the residue solubilized in 10% acetic acid and transferred to a Dowex 50-X8 column. After the column was washed with water and 2m NH₄OH, betaine was eluted by the addition of 4m NH₄OH. The total procedure for obtaining pure radioactive betaine resulted in a yield of 80%. The product obtained was chemically and radiochemically pure, with a specific radioactivity of 54±1 nCi/nmol.     

Measurement of homovanillic acid in urine of newborns and in older children]

In this study, the urinary H.V.A. of new borns and of older children was measured. The urinary H.V.A. titer of the new borns was found to be significantly greater than in older children. Moreover the increase is more pronounced when those infants are born prematurely. Former studies have shown that the metabolism of central nervous system catecholamine reflected by the urinary titers of H.V.A. is as accurate as titers measured in the CSF. Recently several authors have found increased titers of urinary H.V.A. in autistic children. It is therefore possible that the elevated urinary H.V.A. titers in the new born are due to an immaturity of the dopaminergic structures. Blocking these structures provokes an accelerated catecholamine turnover, thereby increasing the levels of catecholamines metabolites (most notably H.V.A.).