Distinctive Fluorescence of Quinacrine-labelled Human <Emphasis Type="Italic">G</Emphasis> Group Chromosomes

HUMAN chromosomes can be identified by their distinctive quinacrine fluorescence pattern¹. We have used this technique to study abnormalities in the G group. Since this report was first submitted, two other reports on the fluorescence of G group chromosomes have been published^2,3.     

An overlooked hybrid between the two diploid <Emphasis Type="Italic">Chenopodium</Emphasis> species in Central Europe determined by microsatellite and morphological analysis

The presence and extent of hybridization within the Chenopodium album aggregate (Amaranthaceae) is still unclear. Although many hybrid combinations have been described, their existence in the field has never been systematically studied and verified. The main aim of this study was to ascertain the extent of interspecific hybridization between the diploid species C. ficifolium and C. suecicum using highly variable nuclear microsatellite markers. Due to the absence of such kind of molecular markers for the whole C. album group, we divided the analysis into two steps: (1) Eleven microsatellite loci designed for the closely related species C. quinoa were cross-amplified in five Eurasian species of the C. album diploid–polyploid complex, i.e. C. album s.s. (6x), C. striatiforme (4x), C. strictum (4x), C. ficifolium (2x) and C. suecicum (2x); (2) For the detection of interspecific hybridization between C. ficifolium and C. suecicum, we sampled 480 individuals from five localities in Central Europe. We also investigated morphological differences between the parental taxa and their hybrid and devised a key for their determination. Analysis of variation in microsatellite loci using Bayesian methods, PCoA and Neighbour-joining tree identified 32 F1 hybrids. These F1 hybrids, described here as C. paradoxum Mandák, formed a cluster between well-differentiated parental species, combining the morphological characters of both their parents. Moreover, genetic analyses also recognized several F2 or backcross hybrids, whose delimitation, mainly from C. suecicum and F1 hybrids, based on morphological characters, is problematic.     

Clinical strains of <Emphasis Type="Italic">Lactobacillus</Emphasis> reduce the filamentation of <Emphasis Type="Italic">Candida albicans</Emphasis> and protect <Emphasis Type="Italic">Galleria mellonella</Emphasis> against experimental candidiasis

Candida albicans is the most common human fungal pathogen and can grow as yeast or filaments, depending on the environmental conditions. The filamentous form is of particular interest because it can play a direct role in adherence and pathogenicity. Therefore, the purpose of this study was to evaluate the effects of three clinical strains of Lactobacillus on C. albicans filamentation as well as their probiotic potential in pathogen-host interactions via an experimental candidiasis model study in Galleria mellonella. We used the reference strain Candida albicans ATCC 18804 and three clinical strains of Lactobacillus: L. rhamnosus strain 5.2, L. paracasei strain 20.3, and L. fermentum strain 20.4. First, the capacity of C. albicans to form hyphae was tested in vitro through association with the Lactobacillus strains. After that, we verified the ability of these strains to attenuate experimental candidiasis in a Galleria mellonella model through a survival curve assay. Regarding the filamentation assay, a significant reduction in hyphae formation of up to 57% was observed when C. albicans was incubated in the presence of the Lactobacillus strains, compared to a control group composed of only C. albicans. In addition, when the larvae were pretreated with Lactobacillus spp. prior to C. albicans infection, the survival rate of G. mellonela increased in all experimental groups. We concluded that Lactobacillus influences the growth and expression C. albicans virulence factors, which may interfere with the pathogenicity of these microorganisms.     

Genetic Regulation of Meiotic Chromosome Pairing by Chromosome 3<Emphasis Type="Italic">D</Emphasis> of <Emphasis Type="Italic">Triticum aestivum</Emphasis>

IN hexaploid wheat (Triticum aestivum, 2n = 6x = 42) the constituent genomes A, B and D derive from closely related diploid species (2n = 2x = 14) within the sub-tribe Triticinae^1–4. The seven different chromosomes of each genome have genetically equivalent (homoeologous) chromosomes in the other two genomes⁵. Homoeologous chromosomes generally compensate each other in nullisomic-tetrasomic combinations⁵.     

Effect of <Emphasis Type="Italic">p</Emphasis>-Chlorophenylalanine on Tryptophan Hydroxylase in Rat Pineal

KOE and Weissman have demonstrated that p-chlorophenylalanine (pCPA) depletes serotonin in the brain of mammals¹. pCPA induces a variety of behaviour changes in rat, cat and other animals^2,3, presumably because of the depletion of serotonin in the brain. The biochemical mechanism of the depletion remains, however, to be elucidated, although it has been proposed that pCPA might inactivate tryptophan hydroxylase in the brain⁴. We demonstrate here that pCPA does not inactivate tryptophan hydroxylase in rat pineal, although pCPA depletes the serotonin level in the pineal.     

Cytogenetic analyses of eight species in the genus <Emphasis Type="Italic">Leptodactylus</Emphasis> Fitzinger, 1843 (Amphibia,Anura, Leptodactylidae), including a new diploid number and a karyotype with multiple translocations

Background

The karyotypes of Leptodactylus species usually consist of 22 bi-armed chromosomes, but morphological variations in some chromosomes and even differences in the 2n have been reported. To better understand the mechanisms responsible for these differences, eight species were analysed using classical and molecular cytogenetic techniques, including replication banding with BrdU incorporation.

Results

Distinct chromosome numbers were found: 2n = 22 in Leptodactylus chaquensis, L. labyrinthicus, L. pentadactylus, L. petersii, L. podicipinus, and L. rhodomystax; 2n = 20 in Leptodactylus sp. (aff. podicipinus); and 2n = 24 in L. marmoratus. Among the species with 2n = 22, only three had the same basic karyotype. Leptodactylus pentadactylus presented multiple translocations, L. petersii displayed chromosome morphological discrepancy, and L. podicipinus had four pairs of telocentric chromosomes. Replication banding was crucial for characterising this variability and for explaining the reduced 2n in Leptodactylus sp. (aff. podicipinus). Leptodactylus marmoratus had few chromosomes with a similar banding patterns to the 2n = 22 karyotypes. The majority of the species presented a single NOR-bearing pair, which was confirmed using Ag-impregnation and FISH with an rDNA probe. In general, the NOR-bearing chromosomes corresponded to chromosome 8, but NORs were found on chromosome 3 or 4 in some species. Leptodactylus marmoratus had NORs on chromosome pairs 6 and 8. The data from C-banding, fluorochrome staining, and FISH using the telomeric probe helped in characterising the repetitive sequences. Even though hybridisation did occur on the chromosome ends, telomere-like repetitive sequences outside of the telomere region were identified. Metaphase I cells from L. pentadactylus confirmed its complex karyotype constitution because 12 chromosomes appeared as ring-shaped chain in addition to five bivalents.

Conclusions

Species of Leptodactylus exhibited both major and minor karyotypic differences which were identified by classical and molecular cytogenetic techniques. Replication banding, which is a unique procedure that has been used to obtain longitudinal multiple band patterns in amphibian chromosomes, allowed us to outline the general mechanisms responsible for these karyotype differences. The findings also suggested that L. marmoratus, which was formerly included in the genus Adenomera, may have undergone great chromosomal repatterning.

     

Molecular cytogenetic characterization of <Emphasis Type="Italic">Triticum timopheevii</Emphasis> chromosomes provides new insight on genome evolution of <Emphasis Type="Italic">T. zhukovskyi</Emphasis>

Triticum timopheevii (2n = 4x = 28, GGA^tA^t) is a tetraploid wheat formerly cultivated in western Georgia. The natural allopolyploid Triticum zhukovskyi is a hexaploid taxon originated from hybridization of T. timopheevii with cultivated einkorn T. monococcum (2n = 2x = 14, A^mA^m). Karyotypically T. timopheevii and T. zhukovskyi differ from other tetraploid and hexaploid wheats and were assigned to the section Timopheevii of the genus Triticum L. Triticum timopheevii and T. zhukovskyi are resistant to many fungal diseases and therefore could potentially be utilized for wheat improvement. We were aiming to precisely identify all T. timopheevii chromosomes and to trace the evolution of T. zhukovskyi. For this, we developed a set of molecular cytogenetic landmarks based on eleven DNA probes. Each chromosome can now be characterized by two to eight probes. The pTa-535 sequence allows the identification of all A^t-genome chromosomes, whereas G-genome and some A^t-genome chromosomes can be identified using (GAA/CTT) _n and pSc119.2 probes. The probes pAesp_SAT86, pAs1, Spelt-1, Spelt-52 and 5S and 45S rDNA can be applied as additional markers to discriminate particular chromosomes or chromosomal regions. The distribution of (GAA/CTT) _n , pTa-535 and pSc119.2 DNA probes on T. timopheevii chromosomes is distinct from other tetraploid wheats and can therefore be used to track individual chromosomes in introgression programs. Our study confirms the origin of T. zhukovskyi from hybridization of T. timopheevii with T. monococcum; however, we show that the emergence was accompanied by changes involving mostly A^t-genome chromosomes. This may be due to the presence of two closely related A-genomes in the T. zhukovskyi karyotype.     

Characterisation of <Emphasis Type="Italic">Thinopyrum bessarabicum</Emphasis> chromosomes through genome-wide introgressions into wheat

Key message

Genome-wide introgressions of Thinopyrum bessarabicum into wheat resulted in 12 recombinant lines. Cytological and molecular techniques allowed mapping of 1150 SNP markers across all seven chromosomes of the J genome.

Abstract

Thinopyrum bessarabicum (2n = 2x = 14, JJ) is an important source for new genetic variation for wheat improvement due to its salinity tolerance and disease resistance. Its practical utilisation in wheat improvement can be facilitated through development of genome-wide introgressions leading to a variety of different wheat–Th . bessarabicum translocation lines. In this study, we report the generation of 12 such wheat–Th . bessarabicum recombinant lines, through two different crossing strategies, which were characterized using sequential single colour and multi-colour genomic in situ hybridization (sc-GISH and mc-GISH), multi-colour fluorescent in situ hybridization (mc-FISH) and single nucleotide polymorphic (SNP) DNA markers. We also detected 13 lines containing different Th. bessarabicum chromosome aberrations through sc-GISH. Through a combination of molecular and cytological analysis of all the 25 lines containing Th. bessarabicum recombinants and chromosome aberrations we were able to physically map 1150 SNP markers onto seven Th. bessarabicum J chromosomes which were divided into 36 segmental blocks. Comparative analysis of the physical map of Th. bessarabicum and the wheat genome showed that synteny between the two species is highly conserved at the macro-level and confirmed that Th. bessarabicum contains the 4/5 translocation also present in the A genome of wheat. These wheat–Th . bessarabicum recombinant lines and SNP markers provide a useful genetic resource for wheat improvement with the latter having a wider impact as a tool for detection of introgressions from other Thinopyrum species containing the J or a closely-related genome such as Thinopyrum intermedium (J^rJ^rJ^vsJ^vsStSt) and Thinopyrum elongatum (E^eE^e), respectively.

     

Location of low copy genes in chromosomes of <Emphasis Type="Italic">Brachiaria</Emphasis> spp.

Repetitive DNA sequences have been widely used in cytogenetic analyses. The use of gene sequences with a low-copy-number, however, is little explored especially in plants. To date, the karyotype details in Brachiaria spp. are limited to the location of rDNA sites. The challenge lies in developing new probes based on incomplete sequencing data for the genus or complete sequencing of related species, since there are no model species with a sequenced genome in Brachiaria spp. The present study aimed at the physical location of conserved genes in chromosomes of Brachiaria ruziziensis, Brachiaria brizantha, and Brachiaria decumbens using RNAseq data, as well as sequences of Setaria italica and Sorghum bicolor through the fluorescent in situ hybridization technique. Five out of approximately 90 selected sequences generated clusters in the chromosomes of the species of Brachiaria studied. We identified genes in synteny with 5S and 45S rDNA sites, which contributed to the identification of chromosome pairs carrying these genes. In some cases, the species of Brachiaria evaluated had syntenic segments conserved across the chromosomes. The use of genomic sequencing data is essential for the enhancement of cytogenetic analyses.     

End-to-End Association of <Emphasis Type="Italic">X</Emphasis> and <Emphasis Type="Italic">Y</Emphasis> Chromosomes in Mouse Meiosis

ACCORDING to the hypothesis of Crew and Koller¹ and Koller and Darlington², there are homologous segments in the X and Y chromosomes of the mouse and other mammals. The homologous regions in the mouse were believed to be localized in the extremely short arms proximal to the kinetochores. The end-to-end association at meiosis was thought to be the result of the formation of a chiasma between these homologous regions³. Electron microscopy revealed a short synaptonemal complex in mouse meiotic cells⁴. However, partial sex linkage has never been demonstrated in the mouse⁵ and other authors^6–10 believe that the X and Y chromosomes associate only by connexion between the chromosome ends furthest from the centromeres.     

<Emphasis Type="Italic">Limnobacter humi</Emphasis> sp. nov., a thiosulfate-oxidizing,heterotrophic bacterium isolated from humus soil,and emended description of the genus <Emphasis Type="Italic">Limnobacter</Emphasis> Spring <Emphasis Type="Italic">et al.</Emphasis> 2001

Three Gram-negative, strictly aerobic, chemolithoheterotrophic bacterial strains, designated UCM-30, UCM-33, and UCM-39^T, were isolated in South Korea. Based on their 16S rRNA gene sequences, the three isolated strains were found to be similar to Limnobacter thiooxidans CS-K2^T (97.41–97.68%), Limnobacter litoralis KP1-19^T (95.55–95.76%), and various genera belonging to the class Betaproteobacteria (90.34–93.34%). DNA-DNA hybridization showed 79.3–83.9% similarity between the genomic DNA of UCM-39^T, UCM-30, and UCM-33, while the sequence similarity between UCM-39^T and L. thiooxidans KACC 13837T or L. litoralis LMG 24869T was 23.7% and 18.6%, respectively. The DNA G+C content of UCM 39T was 59.7 mol%, the major ubiquinone was Q-8, and the optimal oxidation rate was observed at 10 mM thiosulfate. The major fatty acids (≥ 10%) were summed features 3 (C_16:1 ω7c and/or C_16:1 ω6c) and 8 (C_18:1 ω7c and/or C_18:1 ω6c), and C_16:0. The major polar lipids (diphosphatidylglycerol, phosphatidylethanolamine, and phosphatidylglycerol) were found in all members of genus Limnobacter. Based on phenotypic, physiological, and phylogenetic analyses, the UCM-39T strain was found to be significantly distinct to represent a novel species affiliated to the genus Limnobacter. We propose to name it Limnobacter humi sp. nov. with the type strain UCM-39^T (=KACC 18574^T =NBRC 111650^T).     

<Emphasis Type="Italic">Phenylobacterium terrae</Emphasis> sp. nov., isolated from a soil sample of Khyber-Pakhtun-Khwa,Pakistan

A Gram-stain negative, aerobic, motile, non-spore-forming and rod-shaped bacterial strain, designated YIM 730227^T, was isolated from a soil sample, collected from Karak district, Khyber-Pakhtun-Khwa, Pakistan. The bacterium was characterized using a polyphasic taxonomic approach. Pairwise comparison of the 16S rRNA gene sequences showed that strain YIM 730227^T is closely related to Phenylobacterium lituiforme FaiI3^T (97.5% sequence similarity), Phenylobacterium muchangponense A8^T (97.4%), Phenylobacterium panacis DCY109^T (97.1%), Phenylobacterium immobile E^T (97.1%) and Phenylobacterium composti 4T-6^T (97.0%), while also sharing 98.0% sequence similarity with Phenylobacterium hankyongense HKS-05^T after NCBI blast, showing it represents a member of the family Caulobacteraceae. The major respiratory quinone was Q-10 and the major fatty acids were C_16:0, summed feature 8 (comprising C_18:1ω7c and/or C_18:1ω6c), C_18:1ω7c 11-methyl and C_17:0. The polar lipids were phosphatidylglycerol, unidentified glycolipids, phospholipid and unidentified lipid. The G?+?C content of the genomic DNA was 68.2 mol%. The DNA–DNA relatedness values of strain YIM 730227^T with P. hankyongense HKS-05^T, P. lituiforme FaiI3^T, P. muchangponense A8^T, P. panacis DCY109^T, P. immobile E^T and P. composti 4T-6^T were 31.3?±?0.6, 26.1?±?0.2, 24.3?±?0.1, 21.8?±?0.9, 19.8?±?0.6 and 18.2?±?1.1%, respectively, values lower than 70%. Besides the morphological and chemotaxonomic characteristics, phylogenetic analyses of 16S rRNA gene sequences and the biochemical characteristics indicated that the strain YIM 730227^T represents a novel member of the genus Phenylobacterium, for which the name Phenylobacterium terrae sp. nov. (type strain YIM 730227^T =?KCTC62324^T?=?CGMCC 1.16326^T) is proposed.     

<Emphasis Type="Italic">Roseovarius tibetensis</Emphasis> sp. nov., a halophilic bacterium isolated from Lake LongmuCo on Tibetan Plateau

Two Gram-stain negative halophilic strains, designated as LM2^T and LM4, were isolated from Lake LongmuCo on Tibetan Plateau. These two strains were aerobic, catalaseand oxidase-positive, nonmotile and rod-shaped organisms. Phylogenetic analysis based on 16S rRNA gene sequences indicated that LM2^T and LM4 belong to the genus Roseovarius, with Roseovarius tolerans EL-172^T (97.3% and 97.4% 16S rRNA gene sequence similarity, respectively) and Roseovarius azorensis SSW084^T (95.5% and 95.6% 16S rRNA gene sequence similarity, respectively) as their closest neighbors. Q-10 was the sole respiratory quinone of these two strains. The major fatty acids were C_18:1ω7c/C_18:1ω6c, C_16:0, C_19:0 cyclo ω8c, and 11-methyl C_18:1ω7c. The polar lipids included phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, phospholipid of unknown structure containing glucosamine, and unidentified aminolipid. The DNA G + C content was between 64.2 and 64.5 mol%. DNA-DNA hybridization showed 96.7% relatedness between LM2^T and LM4, 24.9% relatedness between LM2^T and R. tolerans EL-172^T, and 36.3% relatedness between LM4 and R. tolerans EL-172^T. Based on phylogenetic analysis, DNA-DNA hybridization, a range of physiological and biochemical characteristics, LM2^T and LM4 belong to the same species and were clearly distinguished from the type strains of the genus Roseovarius. It was evident that LM2^T and LM4 could be classified as a novel species of the genus Roseovarius, for which the name Roseovarius tibetensis sp. nov. is proposed. The type strain is LM2^T (= CGMCC 1.16230^T = KCTC 62028^T).     

Adaptive evolution of osmoregulatory-related genes provides insight into salinity adaptation in Chinese mitten crab, <Emphasis Type="Italic">Eriocheir sinensis</Emphasis>

Osmoregulation is an important mechanism by which euryhaline crustaceans regulate osmotic and ionic concentrations. The Chinese mitten crab (Eriocheir sinensis) is a strong osmoregulating animal model among crustacean species, as it can maintain its hemolymph composition and survives well in either seawater or freshwater. Osmoregulation by E. sinensis during physiological adaptation has been studied extensively. However, the genetic basis of osmoregulation in E. sinensis for acclimating to changing salinities remains unclear. The current study investigated five genes involved in E. sinensis osmoregulation and compared them with a representative marine crab Portunus trituberculatus to test whether adaptive evolution has occurred changing salinity conditions. The results showed that carbonic anhydrase (CA), cytochrome P450 4C (CYP4C), glutamate dehydrogenase (GDH), and the Na⁺/H⁺ exchanger (NHE) have undergone positive selection (i.e., directional selection) in E. sinensis. Thus, the positive selection in CA and NHE suggests that E. sinensis has enhanced capacity for maintaining systemic acid-base balance and ion regulation. GDH and CYP4C also demonstrated positive selection in E. sinensis, suggesting that E. sinensis might have acquired an enhanced capacity to metabolize glutamate and synthesize ecdysteroids in response to a change in osmotic concentration. The present study provides new insight into the molecular genetic basis of salinity adaption in E. sinensis.     

<Emphasis Type="Italic">Spirosoma lituiforme</Emphasis> sp. nov., isolated from soil

A Gram-staining-negative, non-motile, curved rod-shaped, aerobic bacterium, designated S1-2-4^T, was isolated from soil in Jeollabuk-do province, Republic of Korea, and was characterized taxonomically using a polyphasic approach. Comparative 16S rRNA gene sequence analysis showed that strain S1-2-4^T was a member of the family Cytophagaceae and most closely related to ‘Spirosoma radiotolerans’ DG5A (97.2%), Spirosoma fluviale MSd3^T (96.4%), and Spirosoma linguale DSM 74^T (96.3%). The genomic DNA G + C content of strain S1-2-4^T was 49.7 mol%. The major fatty acids were summed feature 3 (C_16:1ω7c/C_16:1ω6c), C_16:1ω5c, and C_16:0, and the major polar lipid was phosphatidylethanolamine. MK-7 was the predominant respiratory quinone. Phenotypic and chemotaxonomic data supported the affiliation of strain S1-2-4^T with the genus Spirosoma. DNA-DNA hybridization between strain S1-2-4^T and ‘Spirosoma radiotolerans’ showed relatively low DNA-DNA relatedness (31%). Strain S1-2-4^T could be distinguished from its closest phylogenetic neighbors based on its phenotypic, genotypic, and chemotaxonomic features. Therefore, strain S1-2-4^T represents a novel member of the genus Spirosoma, for which the name Spirosoma lituiforme sp. nov. is proposed. The type strain is S1-2-4^T (= KCTC 52724^T = JCM 32128^T).     

High-density linkage maps for <Emphasis Type="Italic">Citrus sunki</Emphasis> and <Emphasis Type="Italic">Poncirus trifoliata</Emphasis> using DArTseq markers

The construction of a high-resolution genetic map of citrus would be of great value to breeders and to associate genomic regions with characteristics of agronomic interest. Here, we describe a novel high-resolution map of citrus using a population derived from a controlled cross between Citrus sunki (female parent) and Poncirus trifoliata (male parent). The genetic linkage maps were constructed using DArTseq markers and a pseudo-testcross strategy; only markers showing the expected segregation ratio were considered. To investigate synteny, all markers from both linkage maps were aligned with the genome of Citrus sinensis. The C. sunki map has a total of 2778 molecular markers and a size of 2446.6 cM, distributed across ten linkage groups. The map of P. trifoliata was built with 3084 markers distributed in a total of nine linkage groups, with a total size of 2411.6 cM. These maps are the most saturated linkage maps available for C. sunki and P. trifoliata and have high genomic coverage. We also demonstrated that the maps reported here are closely related to the reference genome of C. sinensis.     

Comparative cytogenetic analysis of four species of <Emphasis Type="Italic">Dendropsophus</Emphasis> (Hylinae) from the Brazilian Atlantic forest

We conducted a cytogenetic study of four hyline frog species (Dendropsophus elegans, D. microps, D. minutus and D. werneri) from southern Brazil. All species had 2n = 30 chromosomes, with interspecific and intraspecific variation in the numbers of metacentric, submetacentric, subtelocentric and telocentric chromosomes. C-banding and fluorochrome staining revealed conservative GC-rich heterochromatin localized in the pericentromeric regions of all species. The location of the nucleolus organizer regions, as confirmed by fluorescent in situ hybridization, differed between species. Telomeric probes detected sites that were restricted to the terminal regions of all chromosomes and no interstitial or centromeric signals were observed. Our study corroborates the generic synapomorphy of 2n = 30 chromosomes for Dendropsophus and adds data that may become useful for future taxonomic revisions and a broader understanding of chromosomal evolution among hylids.     

Mutant tRNA<Superscript>His</Superscript> Ineffective in Repression and Lacking Two Pseudouridine Modifications

TRANSFER RNA has been implicated in the regulation of a number of amino-acid biosynthetic operons^1–4. Histidyl-tRNA^His has been shown to be involved in regulation of the histidine operon by analysis of six genes (hisO, hisR, hisS, hisT, hisU, hisW), mutation of which causes derepression of the enzymes of the histidine biosynthetic pathway in Salmonella typhimurium^5–7. A class of derepressed mutants (hisR) has only about 55% as much tRNA^His as the wild type⁴ and in the one example sequenced, contains tRNA^HIS with a structure identical to that of the wild type⁸. Studies of mutants of the gene for histidyl-tRNA synthetase (hisS) indicated that the derepressed phenotype was associated with defects in the charging of tRNA^HISin vitro². The amounts of charged and uncharged tRNA^His present in vivo during physiological derepression of the wild type and in the six classes of regulatory mutants, have been determined⁹. This work has shown that repression of the histidine operon is correlated directly with the concentration of charged histidyl-tRNA^Hisin vivo and not with the ratio of charged to uncharged or the absolute amount of uncharged tRNA^His. The derepression observed in mutants, of hisS (the gene for histidyl-tRNA synthetase), hisR (the presumed structural gene for the single species of tRNA^His) and hisU and hisW (genes presumably involved in tRNA modification) may be explained by the lower cellular concentration of charged tRNA^His which these mutants contain.     

<Emphasis Type="Italic">Azohydromonas riparia</Emphasis> sp. nov. and <Emphasis Type="Italic">Azohydromonas ureilytica</Emphasis> sp. nov. isolated from a riverside soil in South Korea

White and pale yellow coloured bacteria were isolated from the riverside soil, Daejeon, South Korea, and were designated UCM-11^T, UCM-F25, and UCM-80^T. We found that all strains were able to reduce nitrate, and the cells were aerobic and motile. The DNA G+C contents of UCM-11^T, UCM-F25, and UCM-80^T were between 68.9 to 71.2 mol% and the main ubiquinone was observed as Q-8. Based on16S rRNA gene sequences, strains UCM-11^T and UCM-F25 were found to closely match with Azohydromonas australica IAM 12664^T (98.48–98.55%), and the strain UCM-80^T was the closest match with Azohydromonas lata IAM 12599^T (98.34%). The presence of summed feature 3 (C_16:1 ω7c and/or C_16:1 ω6c), C_16:0, summed feature 8 (C_18:1 ω7c and/or C_18:1 ω6c) as well as twokinds of hydroxyfatty acids consisting of C_10:0 3-OH and C_12:0 2-OH, and branched fatty acids containing C_16:0 iso and C_17:0 cyclo were detected in all the strains. Phosphatidylethanolamine was a major polar lipid. DNA–DNA relatedness confirmed UCM-11^T, UCM-F25 and UCM-80^T as novel members of the genus Azohydromonas. Based on the morphological, physiological, biochemical and genotypic characteristics, we suggest that strains UCM-11^T, UCM-F25, and UCM-80^T represent novel species within the genus Azohydromonas. The names Azohydromonas riparia sp. nov., and Azohydromonas ureilytica sp. nov. are proposed for the type strains UCM-11^T (=KACC 18570^T =NBRC 111646^T) and UCM-80^T (=KACC 18576^T =NBRC 111658^T), respectively.     

How much do we know about hemolytic capability of pathogenic <Emphasis Type="Italic">Candida</Emphasis> species?

Hemolytic factor production by pathogenic Candida species is considered an important attribute in promoting survival within the mammal host through the ability to assimilate iron from the hemoglobin-heme group. Hemolytic capability has been evaluated for Candida species based on hemolysis zones on plate assay, analysis of hemolytic activity in liquid culture medium, and hemolysis from cell-free culture broth. The production of hemolytic factor is variable among Candida species, where C. parapsilosis is the less hemolytic species. In general, no intraspecies differences in beta-hemolytic activities are found among isolates belonging to C. albicans, C. glabrata, C. krusei, C. tropicalis, and C. parapsilosis. The production of hemolytic factor by Candida species is affected by several factors such as glucose supplementation in the culture medium, blood source, presence of erythrocytes and hemoglobin, and presence of electrolytes. On the basis of existing achievements, more researches are still needed in order to extend our knowledge about the biochemical nature of hemolytic molecules produced by distinct Candida species, the mechanism of hemolysis, and the molecular basis of the hemolytic factor expression.