Sequencing and description of the genome of a strain of Stenotrophomonas geniculata isolated from a patient infected with COVID-19 at Hospital Regional No.1 de Charo, Michoacán, México.

Stenotrophomonas is a bacterial genus that can be found in various environments, such as water, soil, and clinical samples. Due to their high genetic and phenotypic diversity, it is difficult to properly identify and classify all isolates. The COVID-19 pandemic caused an increase in nosocomial infections, which played a major role in the high mortality rate among patients in intensive care. This is the first report of the identification of S. geniculata as a nosocomial opportunistic pathogen isolated from a patient with COVID-19. Their genome was isolated, sequenced, and assembled, and it consists of 4,488,090 bp in 24 contigs, 4,103 coding sequences, and a G+C content of 66.58%.

Corn stover induces extracellular laccase activity in Didymosphaeria sp. (syn. = Paraconiothyrium sp.) and exhibits increased in vitro ruminal digestibility when treated with this fungal species.

Fungi can improve stover digestibility due to their ability to secrete oxidative enzymes that depolymerize lignin, allowing the rumen microorganisms to access the polysaccharides of the plant cell wall. Some ascomycetes have shown good delignification capability; however, they have been scarcely evaluated for their ability to improve corn stover (CS) ruminal digestibility. We evaluated the laccase induction by CS of the CMU-196 strain of the ascomycete fungus Didymosphaeria sp. (syn. = Paraconiothyrium sp.). Also, we analyzed the capacity of such strain to modify the cell wall of CS and to improve its digestion by the ruminal microbiota. The CMU-196 strain showed a maximum extracellular laccase activity of 39.74 ± 0.24 U/L when an aqueous stover extract (SE, 10% v/v) was added to the growth medium. The addition of ground stover (GS, 2% w/v) increased the activity to a maximum of 262.27 ± 0.58 U/L. In solid-state fermentation (SSF) assays of GS, the strain degrades cell walls, destabilizing the vessels and tracheids of plant biomass; the protein content reaches a maximum of 33.2 g/kg dry matter (DM) at 70 days, while the crude fiber content shows the highest level of 314 g/kg DM at 14 days. SSF treatment of the CS increased the in vitro ruminal production of gas in a fraction that was considered nondigestible at 18 h, and gas production increased by 14% with respect to the untreated GS at 14 days. The CMU-196 strain can digest the plant cell wall and improve ruminal CS digestibility at a level equivalent to several basidiomycete species.

Typing and selection of wild strains of Trichoderma spp. producers of extracellular laccase.

Using the ITS region and the gene tef1, 23 strains of the genus Trichoderma were identified as belonging to the species T. harzianum (n = 14), T. olivascens (n = 1), T. trixiae (n = 1), T. viridialbum (n = 1), T. tomentosum (n = 2), T. koningii (n = 1), T. atroviride (n = 1), T. viride (n = 1), and T. gamsii (n = 1). Strains expressing extracellular laccase activity were selected by decolorization/oxidation assays in solid media, using azo, anthraquinone, indigoid, and triphenylmethane dyes, and the phenolic substances tannic acid and guaiacol. No strain decolorized Direct Blue 71 or Chicago Blue 6B, but all of them weakly oxidized guaiacol, decolorized Methyl Orange, and efficiently oxidized tannic acid. Based in decolorization/oxidation assays, strains CMU-1 (T. harzianum), CMU-8 (T. atroviride), CMU-218 (T. viride), and CMU-221 (T. tomentosum) were selected for evaluating their extracellular laccase activity in liquid media. Strain CMU-8 showed no basal laccase activity, while strains CMU-1, CMU-218, and CMU-221 had a basal laccase activity of 1,313.88 mU/mL, 763.88 mU/mL, and 799.53 mU/mL, respectively. Addition of sorghum straw inhibited laccase activity in strain CMU-1 by 34%, relative to the basal culture, while strains CMU-8, CMU-21, and CMU-221 increased their laccase activity by 1,321.5%, 64%, and 47%, respectively. These results show that assayed phenolic substrates are good tools for selecting laccase producer strains in Trichoderma. These same assays indicate the potential use of studied strains for bioremediation processes. Straw laccase induction suggests that analyzed strains have potential for straw delignification in biopulping and other biotechnological applications. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:787-798, 2016.