Biochemical characterization of Fsa16295Glu from "Fervidibacter sacchari," the first hyperthermophilic GH50 with β-1,3-endoglucanase activity and founding member of the subfamily GH50_3

The aerobic hyperthermophile "Fervidibacter sacchari" catabolizes diverse polysaccharides and is the only cultivated member of the class "Fervidibacteria" within the phylum Armatimonadota. It encodes 117 putative glycoside hydrolases (GHs), including two from GH family 50 (GH50). In this study, we expressed, purified, and functionally characterized one of these GH50 enzymes, Fsa16295Glu. We show that Fsa16295Glu is a β-1,3-endoglucanase with optimal activity on carboxymethyl curdlan (CM-curdlan) and only weak agarase activity, despite most GH50 enzymes being described as β-agarases. The purified enzyme has a wide temperature range of 4-95°C (optimal 80°C), making it the first characterized hyperthermophilic representative of GH50. The enzyme is also active at a broad pH range of at least 5.5-11 (optimal 6.5-10). Fsa16295Glu possesses a relatively high kcat/KM of 1.82 × 107 s-1 M-1 with CM-curdlan and degrades CM-curdlan nearly completely to sugar monomers, indicating preferential hydrolysis of glucans containing β-1,3 linkages. Finally, a phylogenetic analysis of Fsa16295Glu and all other GH50 enzymes revealed that Fsa16295Glu is distant from other characterized enzymes but phylogenetically related to enzymes from thermophilic archaea that were likely acquired horizontally from "Fervidibacteria." Given its functional and phylogenetic novelty, we propose that Fsa16295Glu represents a new enzyme subfamily, GH50_3.

Thermophilic Dehalococcoidia with unusual traits shed light on an unexpected past

Although the phylum Chloroflexota is ubiquitous, its biology and evolution are poorly understood due to limited cultivability. Here, we isolated two motile, thermophilic bacteria from hot spring sediments belonging to the genus Tepidiforma and class Dehalococcoidia within the phylum Chloroflexota. A combination of cryo-electron tomography, exometabolomics, and cultivation experiments using stable isotopes of carbon revealed three unusual traits: flagellar motility, a peptidoglycan-containing cell envelope, and heterotrophic activity on aromatics and plant-associated compounds. Outside of this genus, flagellar motility has not been observed in Chloroflexota, and peptidoglycan-containing cell envelopes have not been described in Dehalococcoidia. Although these traits are unusual among cultivated Chloroflexota and Dehalococcoidia, ancestral character state reconstructions showed flagellar motility and peptidoglycan-containing cell envelopes were ancestral within the Dehalococcoidia, and subsequently lost prior to a major adaptive radiation of Dehalococcoidia into marine environments. However, despite the predominantly vertical evolutionary histories of flagellar motility and peptidoglycan biosynthesis, the evolution of enzymes for degradation of aromatics and plant-associated compounds was predominantly horizontal and complex. Together, the presence of these unusual traits in Dehalococcoidia and their evolutionary histories raise new questions about the timing and selective forces driving their successful niche expansion into global oceans.

Effect of continuously nebulized ipratropium bromide plus albuterol on emergency department length of stay and hospital admission rates in patients with acute bronchospasm. A randomized, controlled trial

OBJECTIVE

To compare the outcome of patients with acute bronchospasm treated with continuously nebulized albuterol plus ipratropium bromide vs albuterol alone.

SETTING

The Emergency Department (ED) at the University of California San Francisco Medical Center.

PARTICIPANTS

Patients > or = 18 years old presenting to the ED with acute bronchospasm and a peak expiratory flow rate (PEFR) of < 70% predicted.

INTERVENTIONS

This was a prospective, randomized, double-blind, placebo-controlled trial. Subjects were treated with either a combination of albuterol (10 mg/h) plus ipratropium bromide (1.0 mg/h) or albuterol alone via continuous nebulization for a maximum of 3 h. Vital signs, Borg dyspnea score, and PEFR were recorded hourly. Primary outcome measures were improvement in PEFR, hospital admission rates, and length of stay in the ED.

MEASUREMENTS AND RESULTS

Data was analyzed for 67 subjects. The mean age (-/+ SD) was 47.5+/-18.8, and mean initial PEFR was 44.8+/-12.5% of predicted. The median length of stay for all subjects was 225 min, and 31% of all subjects were admitted. Patients given combination therapy averaged 6.3% greater improvement in PEFR compared with control subjects (95% confidence interval [CI], -15% to 27%. The odds ratio for admission with combination therapy was 0.88 (95% CI, 0.28 to 2.8). The median length of stay in the ED was 35 min shorter for those receiving combination treatment (210 vs 245 min; p = 0.03). However, when adjusted for initial PEFR, there was no statistically significant difference (p = 0.26).

CONCLUSION

Although the direction of all three outcome measures favored combination therapy, there was no statistically significant difference between ED patients with acute bronchospasm receiving continuous albuterol plus ipratropium bromide and those receiving albuterol alone.