Abstract:The compositions of bacterial genomes can be changed rapidly and dramatically through a variety of processes including horizontal gene transfer. This form of change is key to bacterial evolution, as it leads to ‘evolution in quantum leaps’. Horizontal gene transfer entails the incorporation of genetic elements transferred from another organism—perhaps in an earlier generation—directly into the genome, where they form ‘genomic islands’, i.e. blocks of DNA with signatures of mobile genetic elements. Genomic isla… Show more
“…Shi and Falkowski 2008), which putatively plays an important role in rapidly changing environments (Rodriguez-Valera et al 2009) and niche partitioning among close relatives (Kopac et al 2014). The shell genome genes do not seem to be randomly dispersed over the chromosome, but rather concentrated within genomic islands with frequent HGT and HR events (Hacker and Carniel 2001;RodriguezValera et al 2009). However, Narechania et al (2012) showed that many core genes have an identical phylogenetic signal as shell genes, which denotes their common evolutionary history.…”
Section: Speciation Factors In (Cyano)bacteriamentioning
The cyanobacteria are the most important prokaryotic primary producers on Earth, inhabiting a great diversity of aquatic and terrestrial environments exposed to light. However, the evolutionary forces leading to their divergence and speciation remain largely enigmatic compared to macroorganisms due to their prokaryotic nature, including vast population sizes, and largely asexual reproduction. The advent of modern molecular techniques has facilitated an understanding of the important factors shaping cyanobacterial evolution, including horizontal gene transfer and homologous recombination. We review the forces shaping the evolution of cyanobacteria and discuss the role of cohesive forces on speciation. Further, while myriad species concepts and definitions are currently used, only a limited subset might be applied to cyanobacteria due to their asexual reproduction. Additionally, concepts based solely on phenotypes provide insufficient resolution. A monophyletic species concept which is universal may be ideal for cyanobacteria. Actual identification of the cyanobacteria is difficult due to cryptic diversity, lack of morphological variability, and frequent convergent evolutionary events. Thus, applied molecular techniques such as DNA barcoding will be useful for identifications of environmental samples. Lastly, we show that the real biodiversity of the cyanobacteria is widely underestimated, due in part to low sampling efforts, sensitivity to the molecular markers
123Biodivers Conserv (2015) 24:739-757 DOI 10.1007 employed, and the species definitions employed by researchers. In conclusion, we anticipate a rapid increase in cyanobacterial taxa described and large revisions of the system in the future as scientists adopt a common approach to cyanobacterial systematics.
“…Shi and Falkowski 2008), which putatively plays an important role in rapidly changing environments (Rodriguez-Valera et al 2009) and niche partitioning among close relatives (Kopac et al 2014). The shell genome genes do not seem to be randomly dispersed over the chromosome, but rather concentrated within genomic islands with frequent HGT and HR events (Hacker and Carniel 2001;RodriguezValera et al 2009). However, Narechania et al (2012) showed that many core genes have an identical phylogenetic signal as shell genes, which denotes their common evolutionary history.…”
Section: Speciation Factors In (Cyano)bacteriamentioning
The cyanobacteria are the most important prokaryotic primary producers on Earth, inhabiting a great diversity of aquatic and terrestrial environments exposed to light. However, the evolutionary forces leading to their divergence and speciation remain largely enigmatic compared to macroorganisms due to their prokaryotic nature, including vast population sizes, and largely asexual reproduction. The advent of modern molecular techniques has facilitated an understanding of the important factors shaping cyanobacterial evolution, including horizontal gene transfer and homologous recombination. We review the forces shaping the evolution of cyanobacteria and discuss the role of cohesive forces on speciation. Further, while myriad species concepts and definitions are currently used, only a limited subset might be applied to cyanobacteria due to their asexual reproduction. Additionally, concepts based solely on phenotypes provide insufficient resolution. A monophyletic species concept which is universal may be ideal for cyanobacteria. Actual identification of the cyanobacteria is difficult due to cryptic diversity, lack of morphological variability, and frequent convergent evolutionary events. Thus, applied molecular techniques such as DNA barcoding will be useful for identifications of environmental samples. Lastly, we show that the real biodiversity of the cyanobacteria is widely underestimated, due in part to low sampling efforts, sensitivity to the molecular markers
123Biodivers Conserv (2015) 24:739-757 DOI 10.1007 employed, and the species definitions employed by researchers. In conclusion, we anticipate a rapid increase in cyanobacterial taxa described and large revisions of the system in the future as scientists adopt a common approach to cyanobacterial systematics.
“…Следует подчеркнуть, что во всех случаях речь идет о геномах конкретных штаммов, а не о видовых геномах, поскольку внутривидовые различия в размерах геномов, в составе и количес-тве генов могут быть значительными [12]. Эти раз-личия обусловлены прежде всего вариабельностью той части генома, которую составляют гены вспомо-гательного (auxiliary [12,48]) или так называемого гибкого (flexible [35]) набора. Более консервативный базовый (core) набор, состоящий из генов «домаш-него хозяйства», обслуживает жизненно-необходи-мые информационные процессы репликации, транс-крипции, трансляции, ключевые пути метаболизма и формирования клеточных структур, определяющих видовую/родовую принадлежность организма.…”
Section: понятие о видовом геномеunclassified
“…Таким образом, интегроны играют роль своеобразных «ловушек», обеспечива-ющих функционирование захваченных кассет, содер-жащих сцепленные гены, контролирующие резистен-тность к лекарственным препаратам, патогенность, синтез ферментов катаболизма и т. п. Особенности структурной организации интегронов и более слож-ных суперинтегронов, рекомбинационные механизмы сборки и перемещения различных интегронов деталь-но рассматриваются в обзорах [2,67]. в геномных островках (ГО) совмещаются раз-личные мобильные элементы и большое число генов, обеспечивающих многокомпонентные процессы, определяющие ключевые черты образа жизни орга-низма хозяина [22,34,35]. Собранные в ГО гены, ответственные за патогенность [22,34,68], биоде-градацию ксенобиотиков [72], симбиогенез [35,63], транспорт металлов и т. д.…”
Section: плазмиды и бактериофаги [4 15 26 70]unclassified
“…в геномных островках (ГО) совмещаются раз-личные мобильные элементы и большое число генов, обеспечивающих многокомпонентные процессы, определяющие ключевые черты образа жизни орга-низма хозяина [22,34,35]. Собранные в ГО гены, ответственные за патогенность [22,34,68], биоде-градацию ксенобиотиков [72], симбиогенез [35,63], транспорт металлов и т. д. (табл.…”
Section: плазмиды и бактериофаги [4 15 26 70]unclassified
“…В хромосоме ГО выявляются по отличию в ГЦ-составе и частоте встречаемости кодонов от остальной части генома, что указывает на попадание ГО в клетку через систе-мы ОГПГ. Островки имеют на флангах специфичес-кие повторы, по которым осуществляется их встраи-вание/вырезание преимущественно в районах генов транспортных РНК [22,35], что снижает опасность нарушения функционально значимых белковых ге-нов базового набора. Особенности процесса интег-рации делают ГО неустойчивыми структурами [35], которые могут элиминироваться из популяции в ус-ловиях, когда снижается селективное значение ГО.…”
Section: плазмиды и бактериофаги [4 15 26 70]unclassified
Horizontal gene transfer as well as mutations, ge- nomic reorganization and gene loss is one of major driving forces of speciation and evolution of bacteria. A notion of definition of "species genome" is presented. The role of various types of mobile elements in distant gene transfer is considered. The nature of barriers for suc- cessful gene transfer on the level of molecular, cell and population processes is uncovered. A special attention is paid to the contribution of different systems of recombination. Hypothesis on the decisive role of horizontal gene transfer in genetic and ecological diversification of bacteria is discussed.
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