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Carbohydrate metabolism via cyclodextrins (CM-CD) is an uncommon starch-converting pathway that thoroughly depends on extracellular cyclomaltodextrin glucanotransferases (CGTases) to transform the surrounding starch substrate to α-(1,4)-linked oligosaccharides and cyclodextrins (CDs). The CM-CD pathway has emerged as a convenient microbial adaptation to thrive under extreme temperatures, as CDs are functional amphipathic toroids with higher heat-resistant values than linear dextrins. Nevertheless, although the CM-CD pathway has been described in a few mesophilic bacteria and archaea, it remains obscure in extremely thermophilic prokaryotes (Topt ≥ 70 °C). Here, a new monophyletic group of CGTases with an exceptional three-domain ABC architecture was detected by (meta)genome mining of extremely thermophilic Thermoanaerobacterales living in a wide variety of hot starch-poor environments on Earth. Functional studies of a representative member, CldA, showed a maximum activity in a thermoacidophilic range (pH 4.0 and 80 °C) with remarkable product diversification that yielded a mixture of α:β:γ-CDs (34:62:4) from soluble starch, as well as G3–G7 linear dextrins and fermentable sugars as the primary products. Together, comparative genomics and predictive functional analysis, combined with data of the functionally characterized key proteins of the gene clusters encoding CGTases, revealed the CM-CD pathway in Thermoanaerobacterales and showed that it is involved in the synthesis, transportation, degradation, and metabolic assimilation of CDs.

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Full plastomes have recently proven to be a valuable data source for resolving recalcitrant phylogenetic relationships in the flowering plant family Bromeliaceae. The study of complete plastomes has additionally led to the discovery of new structural rearrangements and advanced our understanding of bromeliad plastome diversity and evolution. Here, we focus on the study of full plastomes of the bromeliad subfamily Hechtioideae to assess phylogenetic relationships, marker informativeness, and plastome structure and evolution. Using whole‐genome sequencing data, we de novo assembled and annotated new plastid genomes of 19 Hechtioideae species plus one representative each from the Pitcairnioideae and Puyoideae subfamilies and compared them with four additional available plastomes from other bromeliad subfamilies. Our phylogenetic analysis using complete plastome sequences not only recovered the three currently recognized genera of Hechtioideae as monophyletic, strongly supporting Mesoamerantha as sister of Bakerantha and Hechtia, but also improved statistical support at different phylogenetic depths within the subfamily. We identified a set of highly informative loci, some of them explored for the first time in Hechtioideae. Structural rearrangements, including expansions and contractions of the inverted repeats, large inversions, and gene loss and potential pseudogenization were detected mainly within the genus Hechtia. Evolutionary trait rate shifts were associated with the size and guanine–cytosine content of the small single copy and inverted repeats.