Facultad de Ingeniería Química, Universidad Autónoma de Yucatán, Mérida, México.
Evolutionary Genomics Group, Departamento de Producción Vegetal y Microbiología, Universidad Miguel Hernández, Alicante, Spain.
Microbiol Spectr. 2022 Feb 23;10(1):e0231821. doi: 10.1128/spectrum.02318-21. Epub 2022 Jan 5.
Lignocellulose degradation by microbial consortia is multifactorial; hence, it must be analyzed from a holistic perspective. In this study, the temporal transcriptional activity of consortium PM-06, a nixtamalized maize pericarp (NMP) degrader, was determined and related to structural and physicochemical data to give insights into the mechanism used to degrade this substrate. Transcripts were described in terms of metabolic profile, carbohydrate-active enzyme (CAZyme) annotation, and taxonomic affiliation. The PM-06 gene expression pattern was closely related to the differential rates of degradation. The environmental and physiological conditions preceding high-degradation periods were crucial for CAZyme expression. The onset of degradation preceded the period with the highest degradation rate in the whole process, and in this time, several CAZymes were upregulated. Functional analysis of expressed CAZymes indicated that PM-06 overcomes NMP recalcitrance through modular enzymes operating at the proximity of the insoluble substrate. Increments in the diversity of expressed modular CAZymes occurred in the last stages of degradation where the substrate is more recalcitrant and environmental conditions are stressing. Taxonomic affiliation of CAZyme transcripts indicated that Paenibacillus macerans was fundamental for degradation. This microorganism established synergistic relationships with Bacillus thuringiensis for the degradation of cellulose and hemicellulose and with , , and for the saccharification of oligosaccharides. Nixtamalized maize pericarp is an abundant residue of the tortilla industry. Consortium PM-06 efficiently degraded this substrate in 192 h. In this work, the temporal transcriptional profile of PM-06 was determined. Findings indicated that differential degradation rates are important sample selection criteria since they were closely related to the expression of carbohydrate-active enzymes (CAZymes). The initial times of degradation were crucial for the consumption of nixtamalized pericarp. A transcriptional profile at the onset of degradation is reported for the first time. Diverse CAZyme genes were rapidly transcribed after inoculation to produce different enzymes that participated in the stage with the highest degradation rate in the whole process. This study provides information about the regulation of gene expression and mechanisms used by PM-06 to overcome recalcitrance. These findings are useful in the design of processes and enzyme cocktails for the degradation of this abundant substrate.
微生物共生物对木质纤维素的降解是多因素的；因此，必须从整体角度进行分析。在本研究中，测定了共生 PM-06（一种玉米糊化果皮降解物）的时间转录活性，并将其与结构和物理化学数据相关联，以深入了解用于降解该底物的机制。根据代谢谱、碳水化合物活性酶（CAZyme）注释和分类学隶属关系来描述 PM-06 的转录本。PM-06 的基因表达模式与降解的差异速率密切相关。在高降解期之前的环境和生理条件对 CAZyme 表达至关重要。降解的开始先于整个过程中降解率最高的时期，在此期间，几种 CAZymes 上调。表达的 CAZymes 的功能分析表明，PM-06 通过在不溶性底物附近运作的模块化酶克服 NMP 的顽固性。在降解的最后阶段，表达的模块化 CAZymes 的多样性增加，此时底物更顽固，环境条件更具挑战性。CAZyme 转录本的分类学隶属关系表明，巨大芽孢杆菌对降解至关重要。这种微生物与苏云金芽孢杆菌建立了协同关系，用于降解纤维素和半纤维素，与 、 、 用于寡糖的糖化。糊化玉米果皮是玉米饼工业的丰富残渣。共生物 PM-06 在 192 小时内有效地降解了这种底物。在这项工作中，确定了 PM-06 的时间转录谱。研究结果表明，差异降解速率是重要的样品选择标准，因为它们与碳水化合物活性酶（CAZymes）的表达密切相关。降解的初始时间对于消耗糊化果皮至关重要。首次报道了降解开始时的转录谱。接种后，快速转录了多种 CAZyme 基因，产生了不同的酶，参与了整个过程中降解率最高的阶段。本研究提供了有关 PM-06 基因表达调控和克服顽固性机制的信息。这些发现对于设计用于降解这种丰富底物的工艺和酶混合物很有用。
