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El objetivo fue determinar diferencias en la actividad enzimática antioxidante y la concentración de fenoles totales en plantas de limón mexicano (Citrus aurantifolia (Christm.) Swingle), limón persa (Citrus latifolia Tanaka); y naranja dulce Valencia (Citrus sinensis (L.) Osbeck), infectadas bajo condiciones naturales de campo con Candidatus Liberibacter asiaticus (CaLas), en Bustamante, Tamaulipas, México. Se determinó la presencia de CaLas por qPCR; la actividad enzimática de fenilalanina amonio liasa (PAL), que se activa ante el ataque de patógenos; peroxidasa que interviene en la lignificación de paredes como respuesta a la infección; α-amilasa que degrada el almidón y se acumula en el tejido vascular, y compuestos fenólicos que cumplen funciones de defensa. Se realizó un análisis de contrastes. La concentración de proteínas totales mostró diferencias significativas entre especies entre especies (P< 0.0001). Con una media de 6.1 y 6.37 mg de proteínas por g de tejido fresco para árboles infectados de limón mexicano; y naranja dulce negativa a CaLas. La actividad peroxidasa presentó diferencia significativa para limón persa (P=0.0341), con una media de 1.96 U.mg de proteína-<sup>1</sup>. En naranja dulce se observó mayor actividad de α amilasa en los árboles infectados por CaLas (1.19 U.mg de proteína-<sup>1</sup>). La concentración de PAL y fenoles totales no presentaron diferencias significativas entre especies. En el presente estudio se observó que CaLas influye en la actividad enzimática de cítricos.

Abstract Ni.tro.so.cal.da'les. N.L. masc. n. Nitrosocaldus type genus of the order; ‐ ales ending to denote order; N.L. fem. pl. n. Nitrosocaldales the Nitrosocaldus order. Coccoid cells reproduce by binary fission. Thermophilic and neutrophilic. Obligately aerobic. Chemolithoautotrophic growth by ammonia oxidation to nitrite using CO 2 as carbon source. Some members can also use urea as an alternative source of energy for growth. Cell membrane is composed of isoprenoid tetraether lipids, including large amounts of acyclic and cyclized glycerol trialkyl glycerol tetraethers (GTGTs) and crenarchaeol (a unique glycerol dibiphytanyl glycerol tetraether (GDGT) containing one cyclohexane ring and four cyclopentane rings). Fully saturated and monounsaturated menaquinones with six isoprenoid units are present. They are globally distributed in various geothermal environments. Phylogenetic analyses of 16S rRNA and amoA gene sequences place the monophyletic order Ca . Nitrosocaldales as a basal lineage within the phylum Thaumarchaeota . This order can be distinguished from the closest order Nitrososphaerales by a lower mol% G + C content, a higher growth temperature (>60°C), and a higher relative abundance of GTGT. The order Ca . Nitrosocaldales is currently represented by a single family Ca . Nitrosocaldaceae. Type genus : Ca . Nitrosocaldus de la Torre, Walker, Ingalls, Könneke and Stahl 2008, 815. Taxonomic and Nomenclature Notes According to the List of Prokaryotic names with Standing in Nomenclature (LPSN), the taxonomic status of the order Candidatus Nitrosocaldales is: preferred name (not correct name) (last update, February 2025) * . LPSN classification: Archaea / Thermoproteati / Thermoproteota / incertae sedis / Candidatus Nitrosocaldales The order Candidatus Nitrosocaldales can also be recovered in the Genome Taxonomy Database (GTDB) as o__Nitrososphaerales (version v220) ** . GTDB classification: d__Archaea / p__Thermoproteota / c__Nitrososphaeria / o__Nitrososphaerales * Meier‐Kolthoff et al. ( 2022 ). Nucleic Acids Res , 50 , D801 – D807 ; DOI: 10.1093/nar/gkab902 ** Parks et al. ( 2022 ). Nucleic Acids Res , 50 , D785 – D794 ; DOI: 10.1093/nar/gkab776

Abstract Cen.ar.chae'um., Gr. adj. kainos recent, and Gr. adj. koinos common; Gr. adj. archaios ancient; N.L. neut. n. Cenarchaeum = genus of relatively recent (derived nonthermophilic phenotype) and common (non‐“extremophilic”) Archaea. The species Candidatus Cenarchaeum symbiosum of the genus Candidatus Cenarchaeum constitutes the sole archaeal symbiont of the temperate marine sponge Axinella mexicana . It represented the first tractable organism of the so‐called mesophilic crenarchaeota, now Nitrososphaeria, until pure isolates and enrichment cultures became available. It was also the source of the first assembled full genome of the Nitrososphaeria . Physiological and genomic analyses suggest that representatives of this genus are aerobic, psychrophilic, and capable of a chemolithoautotrophic metabolism, by oxidizing ammonia to nitrite. The environmental distribution of the genus so far has been confined to sponge‐associated communities. DNA G + C content (mol%) : 57.74. Type species : Candidatus Cenarchaeum symbiosum Preston, Wu, Molinsky and DeLong 1996, 6246. Taxonomic and Nomenclature Notes According to the List of Prokaryotic names with Standing in Nomenclature (LPSN), the taxonomic status of the genus Candidatus Cenarchaeum is: preferred name (not correct name) (last update, February 2025) * . LPSN classification: Archaea / Thermoproteati / Thermoproteota / Nitrososphaeria / Nitrosopumilales / Nitrosopumilaceae / Candidatus Cenarchaeum The genus Candidatus Cenarchaeum can also be recovered in the Genome Taxonomy Database (GTDB) as g__Cenarchaeum (version v220) ** . GTDB classification: d__Archaea / p__Thermoproteota / c__Nitrososphaeria / o__Nitrososphaerales / f__Nitrosopumilaceae / g__Cenarchaeum * Meier‐Kolthoff et al. ( 2022 ). Nucleic Acids Res , 50 , D801 – D807 ; DOI: 10.1093/nar/gkab902 ** Parks et al. ( 2022 ). Nucleic Acids Res , 50 , D785 – D794 ; DOI: 10.1093/nar/gkab776

Abstract Ni.tro.so.cal.da.ce'ae. N.L. masc. n. Nitrosocaldus type genus of the family; ‐ aceae ending to denote family; N.L. fem. pl. n. Nitrosocaldaceae the Nitrosocaldus family. Cells are irregular cocci and divide by binary fission. Strictly aerobic. Thermophilic, neutrophilic, and lithoautotrophic archaea that are able to gain energy via ammonia oxidation to nitrite. Membrane lipids contain glycerol dibiphytanyl glycerol tetraethers (GDGTs) bound to monoglycosidic, diglycosidic, phosphohexose, and hexose‐phosphohexose headgroups. Like other described Thaumarchaeota , members of this family contain crenarchaeol as a major membrane core lipid. However, their membrane lipids are characterized by the presence of the high abundances of acyclic and cyclized glycerol trialkyl glycerol tetraethers (GTGTs). Respiratory lipoquinones are saturated and monounsaturated menaquinones with six isoprenoid units. Cells and molecular markers have been found in neutral or slightly alkaline geothermal environments, such as hot springs and subsurface gold mines. At present, the family Ca . Nitrosocaldaceae only harbors a single genus, which is so far represented by only one species. Therefore, future phylogenetic analysis of additional cultivated representatives may reveal further subdivisions within the family. DNA G+C content (mol%):36.8–41.7%. Type genus: Candidatus Nitrosocaldus de la Torre, Walker, Ingalls, Könneke and Stahl 2008, 815. Taxonomic and Nomenclature Notes According to the List of Prokaryotic names with Standing in Nomenclature (LPSN), the taxonomic status of the family Candidatus Nitrosocaldaceae is: preferred name (not correct name) (last update, February 2025) * . LPSN classification: Archaea / Thermoproteati / Thermoproteota / incertae sedis / Candidatus Nitrosocaldales / Candidatus Nitrosocaldaceae The family Candidatus Nitrosocaldaceae can also be recovered in the Genome Taxonomy Database (GTDB) as f__Nitrosocaldaceae (version v220) ** . GTDB classification: d__Archaea / p__Thermoproteota / c__Nitrososphaeria / o__Nitrososphaerales / f__Nitrosocaldaceae * Meier‐Kolthoff et al. ( 2022 ). Nucleic Acids Res , 50 , D801 – D807 ; DOI: 10.1093/nar/gkab902 ** Parks et al. ( 2022 ). Nucleic Acids Res , 50 , D785 – D794 ; DOI: 10.1093/nar/gkab776

Abstract Ni.tro.so.cal'dus. N.L. adj. nitrosus nitrous; L. masc. adj. caldus hot; N.L. masc. n. Nitrosocaldus a nitrite producer at thermophilic growth temperatures. Thermophilic, neutrophilic, autotrophic, and aerobic ammonia‐oxidizing archaea. Urea can be used as a source of energy for growth. Cells fix CO 2 via a modified 3‐hydroxypropionate/4‐hydroxybutyrate carbon fixation pathway. Cells are irregular cocci between 0.65 and 0.75 microns in diameter. Cells reproduce by binary fission. Cell membrane lipids consist mainly of acyclic and cyclized glycerol trialkyl glycerol tetraethers (GTGTs) and glycerol dibiphytanyl glycerol tetraethers (GDGTs), with acyclic GTGT and crenarchaeol as the dominant components. Quinone systems include menaquinones with fully saturated and monounsaturated side chains that comprised six isoprenoid units. The members of the genus Ca . Nitrosocaldus can be found in neutral or slightly alkaline terrestrial geothermal environments at temperatures ranging from 65 to 85°C. Phylogenetic analysis on the basis of both 16S rRNA and amoA genes supports the monophyletic genus Ca . Nitrosocaldus within the family Ca . Nitrosocaldaceae. DNA G + C content (mol%) : 37.1. Type species : Ca . Nitrosocaldus yellowstonensis (Nitrosocaldus yellowstonii) de la Torre, Walker, Ingalls, Könneke and Stahl 2008, 815. Taxonomic and Nomenclature Notes According to the List of Prokaryotic names with Standing in Nomenclature (LPSN), the taxonomic status of the genus Candidatus Nitrosocaldus is: preferred name (not correct name) (last update, February 2025) * . LPSN classification: Archaea / Thermoproteati / Thermoproteota / incertae sedis / Candidatus Nitrosocaldales / Candidatus Nitrosocaldaceae / Candidatus Nitrosocaldus The genus Candidatus Nitrosocaldus can also be recovered in the Genome Taxonomy Database (GTDB) as g__Nitrosocaldus (version v220) ** . GTDB classification: d__Archaea / p__Thermoproteota / c__Nitrososphaeria / o__Nitrososphaerales / f__Nitrosocaldaceae / g__Nitrosocaldus * Meier‐Kolthoff et al. ( 2022 ). Nucleic Acids Res , 50 , D801 – D807 ; DOI: 10.1093/nar/gkab902 ** Parks et al. ( 2022 ). Nucleic Acids Res , 50 , D785 – D794 ; DOI: 10.1093/nar/gkab776

Huanglongbing (HLB) is a difficult-to-control and highly destructive citrus disease that, in Brazil, is associated mainly with the bacterium ‘Candidatus Liberibacter asiaticus’ transmitted by the psyllid Diaphorina citri. The aim of this study was to improve our understanding of the ‘Ca. L. asiaticus’ infection process by exposing excised, fully expanded, immature citrus leaves in 50-ml Falcon tubes to one, four, or eight adults from a ‘Ca. L. asiaticus’-exposed colony for 1-, 3-, 7-, or 15-day periods for access to inoculation (IAP). The leaves were incubated at 26°C for 1, 3, 7, 15, and 21 days (incubation period [IP]). Infection frequencies and ‘Ca. L. asiaticus’ titers were assessed by quantitative polymerase chain reaction (qPCR). ‘Ca. L. asiaticus’ infection was a function of leaf age, number of insects, IAP, and IP. In general, higher infection rates were observed on younger leaves inoculated with higher numbers of insects and after longer IAP and IP. The immature excised leaf method allowed determination of 3 to 7 days as the range of time required by ‘Ca. L. asiaticus’ to reach qPCR detectable levels. Even though leaf survival could be prolonged by the maintenance of a branch segment at the base of the leaf petiole, leaf degradation, visible after about 15 days IP, did not allow observation of the entire infection process which, in the intact plant, culminates with the appearance of the blotch mottling symptom on leaf blades.