RESUMO
We have traced the evolution patterns of 2480 transmembrane transporters from five complete genome sequences spanning the entire Hemiascomycete phylum: Saccharomyces cerevisiae, Candida glabrata, Kluyveromyces lactis, Debaryomyces hansenii, and Yarrowia lipolytica. The use of nonambiguous functional and phylogenetic criteria derived from the TCDB classification system has allowed the identification within the Hemiascomycete phylum of 97 small phylogenetic transporter subfamilies comprising a total of 355 transporters submitted to four distinct evolution patterns named "ubiquitous," "species specific," "phylum gains and losses," or "homoplasic." This analysis identifies the transporters that contribute to the emergence of species during the evolution of the Hemiascomycete phylum and may aid in establishing novel phylogenetic criteria for species classification.
Assuntos
Ascomicetos/genética , Proteínas de Transporte/genética , Proteínas de Transporte/metabolismo , Evolução Molecular , Candida albicans/genética , Candida albicans/metabolismo , Candida glabrata , Genoma Fúngico , Kluyveromyces/genética , Kluyveromyces/metabolismo , Proteínas de Membrana Transportadoras/genética , Proteínas de Membrana Transportadoras/metabolismo , Mitocôndrias/metabolismo , Família Multigênica , Proteoma , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Especificidade da Espécie , Yarrowia/genética , Yarrowia/metabolismoRESUMO
Streptococcus thermophilus is a major dairy starter used for the manufacture of yoghurt and cheese. The access to three genome sequences, comparative genomics and multilocus sequencing analyses suggests that this species recently emerged and is still undergoing a process of regressive evolution towards a specialised bacterium for growth in milk. Notably, S. thermophilus has maintained a well-developed nitrogen metabolism whereas its sugar catabolism has been subjected to a high level of degeneracy due to a paucity of carbon sources in milk. Furthermore, while pathogenic streptococci are recognised for a high capacity to expose proteins at their cell surface in order to achieve cell adhesion or to escape the host immune system, S. thermophilus has nearly lost this unique feature as well as many virulence-related functions. Although gene decay is obvious in S. thermophilus genome evolution, numerous small genomic islands, which were probably acquired by horizontal gene transfer, comprise important industrial phenotypic traits such as polysaccharide biosynthesis, bacteriocin production, restriction-modification systems or oxygen tolerance.
Assuntos
Proteínas de Bactérias/genética , Streptococcus thermophilus/genética , Streptococcus thermophilus/fisiologia , Fatores de Virulência/genética , Genoma Bacteriano , Genômica , Streptococcus thermophilus/classificação , Streptococcus thermophilus/patogenicidadeRESUMO
The lactic acid bacterium Streptococcus thermophilus is widely used for the manufacture of yogurt and cheese. This dairy species of major economic importance is phylogenetically close to pathogenic streptococci, raising the possibility that it has a potential for virulence. Here we report the genome sequences of two yogurt strains of S. thermophilus. We found a striking level of gene decay (10% pseudogenes) in both microorganisms. Many genes involved in carbon utilization are nonfunctional, in line with the paucity of carbon sources in milk. Notably, most streptococcal virulence-related genes that are not involved in basic cellular processes are either inactivated or absent in the dairy streptococcus. Adaptation to the constant milk environment appears to have resulted in the stabilization of the genome structure. We conclude that S. thermophilus has evolved mainly through loss-of-function events that remarkably mirror the environment of the dairy niche resulting in a severely diminished pathogenic potential.
