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PubMed1999

Phylogenetic diversity, polyamine pattern and DNA base composition of members of the order Planctomycetales.

The 16S rDNA sequences of 20 novel isolates of members of the order Planctomycetales were compared to those of the type strains of described planctomycete species and 22 planctomycete isolates for which the 16S rDNA sequences had been previously determined. The novel isolates could be assigned to several phylogenetically broad groups, four of which are defined by the genera Gemmata, Isosphaera, Planctomyces and Pirellula. To evaluate polyamines as a chemotaxonomic marker within this order, the polyamine pool was determined for six planctomycete reference species and for 20 planctomycete isolates. All analysed members of the order Planctomycetales contained significant amounts of polyamines. sym-Homospermidine (HSPD) is present in all strains except Planctomyces limnophilus and related strains, which had high amounts of putrescine (PUT) as the dominant polyamine component. The distribution of PUT, HSPD and spermidine reflects the phylogenetic diversity within the Planctomycetales as closely related representatives of the phylogenetic groups defined by described species and novel isolates exhibit similar polyamine patterns. Determination of the DNA base composition revealed G + C contents of > 60 mol% for members of Gemmata and Isosphaera whereas, except for two isolates, strains which are phylogenetically associated with Planctomyces and Pirellula had G + C contents of 51-57 mol%.

Bacteria↗
PubMed1999

A protein-based phylogenetic tree for gram-positive bacteria derived from hrcA, a unique heat-shock regulatory gene.

The dnaK operon from Bacillus subtilis and other Gram-positive bacteria with low G + C DNA content contains additional heat-shock genes, including hrcA. The hrcA gene encodes a transcription factor that negatively regulates heat-shock genes and is uniformly present in all Gram-positive bacteria studied to date. An hrcA homologue is also present in Synechocystis species, Leptospira interrogans, Chlamydia trachomatis, Caulobacter crescentus and Methanococcus jannaschii, organisms that diverged early on from the common ancestor of all Gram-positive bacteria and Proteobacteria, according to 16S rRNA phylogeny. A partial, protein-based phylogenetic tree, derived using amino acid sequence homology of hrcA proteins from Gram-positive bacteria, is presented here, and the results are compared with the phylogenetic trees generated from 16S rRNA, dnaK and dnaJ sequences. The location of the hrcA gene and the genome organization of the dnaK operon support the division of all Gram-positive bacteria into three major groups: one group contains high-G + C Gram-positive bacteria, and two others contain low-G + C Gram-positive bacteria. Among the Gram-positive bacteria with low G + C DNA content, the results indicate that there is a close phylogenetic relationship between Bacillus species and Clostridium species on the one hand and between Lactococcus lactis and Streptococcus mutans on the other. Streptomyces and Mycobacterium species also exhibited a close relationship. A hierarchical arrangement of Gram-positive bacteria based on HrcA sequences is proposed as an additional refinement of the phylogenetic relationships within this important bacterial group.

Amino Acid Sequence↗
PubMed1999

Comparison of partial malolactic enzyme gene sequences for phylogenetic analysis of some lactic acid bacteria species and relationships with the malic enzyme.

DNA sequences covering 36% of the mle gene that encodes the malolactic enzyme were determined for 13 strains of lactic acid bacteria, representing Pediococcus, Leuconostoc, Lactobacillus and Oenococcus genera. The sequences were aligned with the corresponding region of mleS in Lactococcus lactis. The phylogenetic distance matrix tree of all mle sequences was compared with the 16S rRNA phylogenetic tree. The analysis showed that the mle fragment evolved more rapidly than the 16S gene and differently. Pediococcus and Lactobacillus species were intermixed in the 16S rRNA tree whereas they were separated in the mle tree. Leuconostoc mesenteroides and Oenococcus oeni were distinct from other species in the 16S rRNA tree, whereas they were intermixed with Lactobacillus species and Lactococcus lactis in the mle tree. The amino acid sequences deduced from partial mle genes were aligned with 22 malic enzyme sequences and the corresponding phylogenetic tree was constructed. Malic and malolactic enzymes were distinct at the phylogenetic level, except for malic enzymes of yeast and Escherichia coli which were nearer the malolactic enzymes than the other malic enzymes. The analysis of conserved sites showed several interesting amino acids specific to either malic enzyme or malolactic enzyme.

Amino Acid Sequence↗
PubMed2000

Phylogenetic analysis of the genus Thermoactinomyces based on 16S rDNA sequences.

The almost complete 16S rDNA sequences of the type strains of eight validly described species and two invalid species of the genus Thermoactinomyces were determined and phylogenetically analysed. The validly described Thermoactinomyces species formed phylogenetic lineages related to the family Bacillaceae, as shown previously. However, the available strains of 'Thermoactinomyces glaucus' and 'Thermoactinomyces monosporus' exhibited their closest phylogenetic affinities not to the genus Thermoactinomyces but to the genus Saccharomonospora. Some Thermoactinomyces species were shown to be closely related from 16S rDNA sequence analysis. Particularly, Thermoactinomyces vulgaris KCTC 9076T and Thermoactinomyces candidus KCTC 9557T had the same 16S rDNA sequences and Thermoactinomyces thalpophilus KCTC 9789T and Thermoactinomyces sacchari KCTC 9790T showed 16S rDNA similarity value of almost 100%. From phylogenetic analysis based on 16S rDNA sequences, it is suggested that the genus Thermoactinomyces should be taxonomically re-evaluated using other useful taxonomic markers.

DNA, Bacterial↗
PubMed2000

Phylogenetic analysis of members of the genus Rickettsia using the gene encoding the outer-membrane protein rOmpB (ompB).

To confirm the phylogenetic analysis previously inferred by comparison of the citrate synthase and rOmpA gene sequences (gitA and ompA, respectively), the rOmpB gene (ompB) of 24 strains of the genus Rickettsia was amplified and sequenced. rOmpB is an outer-membrane protein of high molecular mass, the presence of which can be demonstrated in most rickettsiae by immunological cross-reactivity in Western blots. No PCR amplification was obtained with Rickettsia bellii or Rickettsia canadensis. For the other rickettsiae, phylogenetic analysis was inferred from the comparison of both the gene and derived protein sequences by using parsimony, maximum-likelihood and neighbour-joining methods which gave the same organization. All nodes were well supported (>86% bootstrap values), except in the cluster including Rickettsia africae strain S and Rickettsia parkeri, and this analysis confirmed the previously established phylogeny obtained from combining results from gltA and ompA. Based on phylogenetic data, the current classification of the genus Rickettsia is inappropriate, specifically its division into two groups, typhus and spotted fever. Integration of phenotypic, genotypic and phylogenetic data will contribute to the definition of a polyphasic taxonomy as has been done for other bacterial genera.

Bacterial Outer Membrane Proteins↗
PubMed2000

What is the phylogenetic position of Cryptosporidium?

The phylogenetic position of Cryptosporidium is elusive. Although previous studies based solely upon small-subunit (SSU) rRNA sequences suggested that the genus was an early emerging lineage among the Apicomplexa, bootstrap support for this placement was low. Here, the phylogenetic position of Cryptosporidium has been re-evaluated for SSU rRNA, fused SSU/large-subunit (LSU) rRNA and six protein sequences using traditional distance-based neighbour-joining, maximum-parsimony and maximum-likelihood methods of phylogenetic reconstruction as well as the new Slow-Fast analysis, which focuses upon the slowly evolving positions within sequences and is especially useful if a long-branch attraction (LBA) artefact is suspected. All the methods of reconstruction indicated a trend for the early emergence of Cryptosporidium at the base of the Apicomplexa and showed that an LBA artefact plays no role in this placement. Although the inclusion of additional numbers of neither species nor genes has significantly enhanced the bootstrap support for this phylogenetic position, recent biochemical, molecular and ultrastructural data are congruent with it. Therefore, we favour a working hypothesis that this genus constitutes an early emerging branch of the Apicomplexa.

Animals↗
PubMed2000

Comparative phylogenetic analyses of members of the order Planctomycetales and the division Verrucomicrobia: 23S rRNA gene sequence analysis supports the 16S rRNA gene sequence-derived phylogeny.

Almost complete 23S rRNA gene sequences were obtained from 13 planctomycete strains, the fimbriated, prosthecate bacterium Verrucomicrobium spinosum and two strains of the genus Prosthecobacter. The 23S rRNA genes were amplified by the PCR, using modified primers. The majority of the planctomycete strains investigated were shown to have 23S rRNA genes that were not linked to the 16S rRNA genes. Amplification of the 5'-termini of these genes was achieved using a novel primer-design strategy. Comparative phylogenetic analyses were performed using the 23S rRNA gene sequences determined in this study and previously determined 16S rRNA gene sequences. The phylogenetic dendrograms constructed from both datasets showed that the planctomycetes form a coherent group and distinct lineage within the domain Bacteria. Analysis of 23S rRNA gene sequences of Verrucomicrobium spinosum, Prosthecobacter fusiformis and Prosthecobacter sp. strain FC-2 showed that these organisms cluster together, as was also shown here and previously by analysis of 16S rRNA gene sequences. The distinct phylogenetic position of the division Verrucomicrobia was also supported by analysis of the 23S rRNA gene sequences, and no statistically significant phylogenetic relationship between the division Verrucomicrobia and the planctomycetes was found. The analyses presented in this study also provide further evidence that the chlamydiae are no more related to members of the order Planctomycetales and the division Verrucomicrobia than they are to members of other bacterial lineages.

Bacteria↗
PubMed2001

Construction and bootstrap analysis of DNA fingerprinting-based phylogenetic trees with the freeware program FreeTree: application to trichomonad parasites.

The Win95/98/NT program FreeTree for computation of distance matrices and construction of phylogenetic or phenetic trees on the basis of random amplified polymorphic DNA (RAPD), RFLP and allozyme data is presented. In contrast to other similar software, the program FreeTree (available at http://www.natur.cuni.cz/~flegr/programs/freetree or http://ijs.sgmjournals.org/content/vol51/issue3/) can also assess the robustness of the tree topology by bootstrap, jackknife or operational taxonomic unit-jackknife analysis. Moreover, the program can be also used for the analysis of data obtained in several independent experiments performed with non-identical subsets of taxa. The function of the program was demonstrated by an analysis of RAPD data from 42 strains of 10 species of trichomonads. On the phylogenetic tree constructed using FreeTree, the high bootstrap values and short terminal branches for the Tritrichomonas foetus/suis 14-strain branch suggested relatively recent and probably clonal radiation of this species. At the same time, the relatively lower bootstrap values and long terminal branches for the Trichomonas vaginalis 20-strain branch suggested more ancient radiation of this species and the possible existence of genetic recombination (sexual reproduction) in this human pathogen. The low bootstrap values and the star-like topology of the whole Trichomonadidae tree confirm that the RAPD method is not suitable for phylogenetic analysis of protozoa at the level of higher taxa. It is proposed that the repeated bootstrap analysis should be an obligatory part of any RAPD study. It makes it possible to assess the reliability of the tree obtained and to adjust the amount of collected data (the number of random primers) to the amount of phylogenetic signals in the RAPD data of the taxon analysed. The FreeTree program makes such analysis possible.

Animals↗
PubMed2001

Phylogenetic diversity of Klebsiella pneumoniae and Klebsiella oxytoca clinical isolates revealed by randomly amplified polymorphic DNA, gyrA and parC genes sequencing and automated ribotyping.

The infra-specific phylogenetic diversity and genetic structure of both Klebsiella pneumoniae and Klebsiella oxytoca was investigated using a combination of randomly amplified polymorphic DNA (RAPD) analysis, sequencing of gyrA and parC genes, and automated ribotyping. After RAPD analysis with four independent primers of 120 clinical isolates collected from 22 European hospitals in 13 countries, K. pneumoniae isolates fell into three clusters and K. oxytoca isolates fell into two clusters, while Klebsiella planticola isolates formed a sixth cluster. Each cluster was geographically widespread. K. pneumoniae cluster I (KpI) accounted for 80% of the isolates of this species and included reference strains of the three subspecies K. pneumoniae subsp. pneumoniae, K. pneumoniae subsp. ozaenae and K. pneumoniae subsp. rhinoscleromatis. Clusters KpII and KpIII were equally represented, as were the two K. oxytoca clusters. Individualization of each cluster was fully confirmed by phylogenetic analysis of gyrA and parC gene sequences. In addition, sequence data supported the evolutionary separation of K. pneumoniae from a phylogenetic group including K. oxytoca, Klebsiella terrigena, K. planticola and Klebsiella ornithinolytica. Automated ribotyping using Mlu I appeared suitable for identification of each Klebsiella cluster. The adonitol fermentation test was found to be useful for cluster identification in K. pneumoniae, since it was negative in all strains of clusters KpIII and in some KpII strains, but always positive in cluster KpI. The usefulness of gyrA and parC sequence data for population genetics and cluster identification in bacteria was demonstrated, even for the phylogenetic positioning of quinolone-resistant isolates.

DNA Gyrase↗
PubMed2002

Phylogenetic analysis of the genus Pediococcus, including Pediococcus claussenii sp. nov., a novel lactic acid bacterium isolated from beer.

Pediococci are found in foods and on plants and as beer-spoilage agents. The goal of the present study was to use the DNA sequences of the first three variable regions of the 165 rRNA gene, the 16S-23S rRNA internally transcribed spacer region sequence and approximately a third of the 60 kDa heat-shock protein gene to elucidate phylogenetic groupings within the genus Pediococcus. Phylogenetic trees were created with sequence data from 31 Pediococcus and three Lactobacillus isolates. Complete 16S rRNA gene sequences from selected Pediococcus isolates were also examined. The results were interpreted in relation to the currently accepted Pediococcus species. We found that, where previously done, speciation of many Pediococcus isolates is inaccurate. Also, one grouping of seven isolates did not include any currently recognized Pediococcus species type isolate. Our phylogenetic analyses support the conclusion that these seven isolates, all of brewing spoilage origin, belong to a novel species, for which the name Pediococcus claussenii sp. nov. is proposed (type strain P06(T0 = ATCC BAA-344(T) = DSM 14800(T)). Phylogenetic analysis has therefore helped to resolve problems surrounding species identification of Pediococcus isolates.

Base Composition↗
PubMed1992

Analysis of a new hepatitis C virus type and its phylogenetic relationship to existing variants.

Sequences obtained in the 5' non-coding region (5'NCR) of hepatitis C virus (HCV) were obtained from Scottish blood donors and compared with previously published HCV sequences. Phylogenetic analysis revealed the existence of three distinct groups of sequences; two of these corresponded to the recently described HCV types 1 and 2 variants, while viral sequences detected in around a third of the blood donors formed a separate phylogenetic group that probably represents infection with a novel virus species. Nucleotide sequences of this latter group differed from all previously published 5'NCR sequence variants by at least 9%. This new virus type also differed considerably from previously published variants in other regions of the viral genome (core, NS-3 and NS-5), with corrected nucleotide distances of 15, 43 and 49% respectively from the prototype HCV-1 sequence. Formal phylogenetic analysis of each of the coding regions confirmed that HCV type 1 variants could be clearly differentiated into regional variants (Far East and U.S.A./European), in contrast to the clearly overlapping geographical distributions of the main HCV types in U.K. blood donors. We discuss the evidence for and against the hypothesis that the three main phylogenetic groups identified in this study represent separate species of HCV.

Amino Acid Sequence↗
PubMed1997

Phylogenetic analysis of pestiviruses from domestic and wild ruminants.

Infections with pestiviruses occur in cattle, sheep, pigs and also in numerous other ungulate species. In the present study, pestiviruses from goat, buffalo, deer and giraffe were analysed at the molecular level; unusual strains from cattle and pigs were also included. A phylogenetic analysis of the respective pestiviruses was undertaken on the basis of a fragment from the 5' noncoding region as well as the gene encoding autoprotease Npro. Statistical analyses of the respective phylogenetic trees-based on the 5' NCR revealed low confidence levels for most of the branches, while the structure of the tree based on the Npro gene was supported by high bootstrap values. Accordingly, the isolates from goat, buffalo and deer can be grouped together with bovine viral diarrhoea virus (pestivirus type 1); within this genotype three subgroups and one disparate virus have been identified. One isolate from pig and one from cattle belong to the group of 'true' border disease virus (pestivirus type 3), which can be further subdivided into two major subgroups. Interestingly, the giraffe isolate does not belong to one of the four established pestivirus genotypes. The phylogenetic analysis strongly suggests that genotype 1 pestiviruses occur world-wide in many ruminant species. Furthermore, phylogenetic trees based on the Npro gene nucleotide sequences show that the respective sequences do not segregate into discrete lineages based on host-species origin.

Amino Acid Sequence↗
PubMed2000

Phylogenetic analysis of the three polymerase genes (PB1, PB2 and PA) of influenza B virus.

Phylogenetic patterns of the three polymerase (PB2, PB1 and PA) genes of a total of 20 influenza B viruses isolated during a 58 year period, 1940-1998, were analysed in detail in a parallel manner. All three polymerase genes consistently showed evolutionary divergence into two major distinct lineages and their amino acid profiles demonstrated conserved lineage-specific substitutions. Dendrogram topologies of the PB2 and PB1 genes were very similar and contrasted with that of the PA gene. It was of particular interest to reveal that even though the PA gene evolved into two major lineages, that of three recent Asian Victoria/1/87-like strains formed a branch cluster located in the same lineage as that of recent Yamagata/16/88-like isolates. Differences in the phylogenetic pathways of three polymerase genes were not only a reflection of genetic reassortment between co-circulating influenza B viruses, but also an indication that the polymerase genes were not co-evolving as a unit. As a result, comparison of the phylogenetic patterns of the three polymerase genes with previously determined patterns of the HA, NP, M and NS genes of 18 viruses defined the existence of eight distinct genome constellations. Also, similar phylogenetic profiles among the PA, NP and M genes, as well as between the PB2 and PB1 genes, were observed, suggesting possible functional interactions among these proteins. Completion of evolutionary analysis of the six internal genes and the HA gene of influenza B viruses revealed frequent genetic reassortment among co-circulating variable strains and suggested co-dependent evolution of genes.

Amino Acid Sequence↗
PubMed2000

Phylogenetic relationships of Pleurotus species according to the sequence and secondary structure of the mitochondrial small-subunit rRNA V4, V6 and V9 domains.

A comparative study of the V4, V6 and V9 domains of the mitochondrial small-subunit (SSU) rRNA was conducted to evaluate the use of these sequences to investigate phylogenetic relatedness within the genus Pleurotus. The PCR products encompassing these regions from 48 isolates belonging to 16 Pleurotus species were sequenced and compared. From this comparison, the length and sequence of the three domains were found to be constant within a species. Significant inter-species variations due to insertion/deletion events were found, in most cases occurring in regions not directly involved in the maintainance of the standard SSU rRNA secondary structure. Phylogenetic analysis based upon these mitochondrial sequences was in agreement with relationships previously established by morphological descriptions and with previous studies based upon the nuclear genome or isozymes; moreover such analysis resolved some ambiguities in earlier analyses. It was confirmed that P. ostreatus and P. florida represent a single species, as well as P. pulmonarius and P. sajor-caju. The phylogenetic analysis also made it possible to assess the relative positions of P. rattenburyi, P. lampas, P. sapidus, P. colombinus and P. eryngii. The results clearly showed that sequences of the V4, V6 and V9 domains of the mitochondrial SSU rRNA could provide good markers for use in the taxonomy and phylogeny of species of Basidiomycota. Because of their nucleotide conservation, the major advantage of these species-specific markers was the possibility to study only one isolate from each species to determine phylogenetic relatedness.

Base Sequence↗
PubMed2004

Phylogenetic analysis of gastric and enterohepatic Helicobacter species based on partial HSP60 gene sequences.

Analysis of 16S rRNA gene sequences has been the method generally used to study the evolution and phylogeny of bacteria. Phylogenetic analysis of the 16S rRNA gene has shown the position of the genus Helicobacter in the epsilon-subclass of the Proteobacteria. Because 16S rRNA-based phylogeny does not always correspond to the results of polyphasic taxonomy, and the related species cannot always be separated, new phylogenetic markers for Helicobacter species are needed. In this study, conserved partial (600 bp) 60 kDa heat-shock protein (HSP60) sequences were used to study the phylogeny of 37 strains of gastric and enterohepatic Helicobacter species, including type strains of 15 Helicobacter species with validly published names, reference strains of flexispira taxa and Helicobacter felis, Helicobacter bizzozeronii and Helicobacter salomonis and canine flexispira strains. The partial HSP60 gene sequence proved to be a useful phylogenetic marker for the genus Helicobacter, providing a means of differentiating all 15 Helicobacter species analysed. In the resulting phylogenetic tree, gastric Helicobacter species and enterohepatic species with flexispira morphology formed tight, separate clusters. In general, HSP60 sequence similarities between Helicobacter species were significantly lower than the corresponding 16S rRNA gene sequence similarities, indicating a better resolution for species identification. In addition, a specific PCR method for identifying H. salomonis was developed based on the partial HSP60 sequence.

Animals↗
PubMed2004

Dissection of phylogenetic relationships among 19 rapidly growing Mycobacterium species by 16S rRNA, hsp65, sodA, recA and rpoB gene sequencing.

The current classification of non-pigmented and late-pigmenting rapidly growing mycobacteria (RGM) capable of producing disease in humans and animals consists primarily of three groups, the Mycobacterium fortuitum group, the Mycobacterium chelonae-abscessus group and the Mycobacterium smegmatis group. Since 1995, eight emerging species have been tentatively assigned to these groups on the basis of their phenotypic characters and 16S rRNA gene sequence, resulting in confusing taxonomy. In order to assess further taxonomic relationships among RGM, complete sequences of the 16S rRNA gene (1483-1489 bp), rpoB (3486-3495 bp) and recA (1041-1056 bp) and partial sequences of hsp65 (420 bp) and sodA (441 bp) were determined in 19 species of RGM. Phylogenetic trees based upon each gene sequence, those based on the combined dataset of the five gene sequences and one based on the combined dataset of the rpoB and recA gene sequences were then compared using the neighbour-joining, maximum-parsimony and maximum-likelihood methods after using the incongruence length difference test. Combined datasets of the five gene sequences comprising nearly 7000 bp and of the rpoB+recA gene sequences comprising nearly 4600 bp distinguished six phylogenetic groups, the M. chelonae-abscessus group, the Mycobacterium mucogenicum group, the M. fortuitum group, the Mycobacterium mageritense group, the Mycobacterium wolinskyi group and the M. smegmatis group, respectively comprising four, three, eight, one, one and two species. The two protein-encoding genes rpoB and recA improved meaningfully the bootstrap values at the nodes of the different groups. The species M. mucogenicum, M. mageritense and M. wolinskyi formed new groups separated from the M. chelonae-abscessus, M. fortuitum and M. smegmatis groups, respectively. The M. mucogenicum group was well delineated, in contrast to the M. mageritense and M. wolinskyi groups. For phylogenetic organizations derived from the hsp65 and sodA gene sequences, the bootstrap values at the nodes of a few clusters were <70 %. In contrast, phylogenetic organizations obtained from the 16S rRNA, rpoB and recA genes were globally similar to that inferred from combined datasets, indicating that the rpoB and recA genes appeared to be useful tools in addition to the 16S rRNA gene for the investigation of evolutionary relationships among RGM species. Moreover, rpoB gene sequence analysis yielded bootstrap values higher than those observed with recA and 16S rRNA genes. Also, molecular signatures in the rpoB and 16S rRNA genes of the M. mucogenicum group showed that it was a sister group of the M. chelonae-abscessus group. In this group, M. mucogenicum ATCC 49650(T) was clearly distinguished from M. mucogenicum ATCC 49649 with regard to analysis of the five gene sequences. This was in agreement with phenotypic and biochemical characteristics and suggested that these strains are representatives of two closely related, albeit distinct species.

Bacterial Proteins↗
PubMed2005

Phylogenetic positions of 'Candidatus Phytoplasma asteris' and Spiroplasma kunkelii as inferred from multiple sets of concatenated core housekeeping proteins.

Phytopathogenic mollicutes, which include spiroplasmas and phytoplasmas, are cell wall-less bacteria that parasitize plant hosts and insect vectors. Knowledge of the evolution of these agents is important in understanding their biology. The availability of the first complete phytoplasma and several partial spiroplasma and phytoplasma genome sequences made possible an investigation of evolutionary relationships between phytopathogenic mollicutes and other micro-organisms, especially Gram-positive bacteria, using a comparative genomics approach. Genome data from a total of 41 bacterial species were used in the analysis. Sixty-one conserved proteins were selected from each species for the construction of a hypothetical phylogenetic tree. The genes encoding these selected proteins are among a core of genetic elements that constitute a hypothetical minimal genome. The proteins were concatenated into five superproteins according to their functional categories, and phylogenetic trees were reconstructed using distance, parsimony and likelihood methods. Phylogenetic trees based on the five sets of concatenated proteins were congruent in both clade topology and relative branching length. Spiroplasma kunkelii and phytoplasmas clustered together with other mollicutes, forming a monophyletic group. Phytoplasmas diverged from spiroplasmas and mycoplasmas at early stages in the evolution of mollicutes. Branch lengths on the phylogenetic trees were noticeably longer in the Mollicutes clade, suggesting that the genes encoding the five sets of proteins evolved at a greater rate in this clade than in other clades. This observation reinforces the concept that mollicutes have rapidly evolving genomes.

Bacterial Proteins↗
PubMed2003

Extracting phylogenetic information from whole-genome sequencing projects: the lactic acid bacteria as a test case.

The availability of an ever increasing number of complete genome sequences of diverse prokaryotic taxa has led to the introduction of novel approaches to infer phylogenetic relationships among bacteria. In the present study the sequences of the 16S rRNA gene and nine housekeeping genes were compared with the fraction of shared putative orthologous protein-encoding genes, conservation of gene order, dinucleotide relative abundance and codon usage among 11 genomes of species belonging to the lactic acid bacteria. In general there is a good correlation between the results obtained with various approaches, although it is clear that there is a stronger phylogenetic signal in some data sets than in others, and that different parameters have different taxonomic resolutions. It appears that trees based on different kinds of information derived from whole-genome sequencing projects do not provide much additional information about the phylogenetic relationships among bacterial taxa compared to more traditional alignment-based methods. Nevertheless, it is expected that the study of these novel forms of information will have its value in taxonomy, to determine which genes are shared, when genes or sets of genes were lost in evolutionary history, to detect the presence of horizontally transferred genes and/or confirm or enhance the phylogenetic signal derived from traditional methods. Although these conclusions are based on a relatively small data set, they are largely in agreement with other studies and it is anticipated that similar trends will be observed when comparing other genomes.

Bacterial Proteins↗