Cross-resistance relationships in Escherichia coli between ultraviolet radiation and nitrous acid

Zampieri, Antonio (Palo Alto Medical Research Foundation, Palo Alto, Calif.), and Joseph Greenberg. Cross-resistance relationships in Escherichia coli between ultraviolet radiation and nitrous acid. J. Bacteriol. 87:1094-1099. 1964.-A number of radiosensitive and radioresistant strains of Escherichia coli were tested for sensitivity to injury by nitrous acid. All the radioresistant strains, including 13 radioresistant mutants of strain S, B/r, Bpr5, and K-12, were found to be significantly more resistant to nitrous acid than were the radiosensitive strains S and B. The radioresistant mutants of strain S, Bpr5, and K-12 displayed similar responses to nitrous acid and were less resistant than was strain B/r. Strains B and S were indistinguishable on the basis of nitrous acid sensitivity. The survival curves of all strains examined were similar in shape to corresponding survival curves after ultraviolet radiation. The sensitivity to nitrous acid of the radiosensitive strains S and B, but not that of the radioresistant strains, was found to be greater on Tryptone medium than on Penassay medium, and greater on Penassay medium than on glucose-salts medium. Between 2 and 3% of the strain S survivors of nitrous acid treatment were radioresistant; 46 such radioresistant mutants were isolated and found to be identical in cross-resistance pattern with radioresistant types (R(3), R(4), or R(6)) previously described. The proportions in which these radioresistant types were found to occur were similar to those observed after selection by other radiomimetic agents.     

Tracing paternal ancestry in mice, using the Y-linked, sex-determining locus, Sry

The molecular evolution of mammalian Y-linked DNA sequences is of special interest because of their unique mode of inheritance: most Y- linked sequences are clonally inherited from father to son. Here we investigate the use of Y-linked sequences for phylogenetic inference. We describe a comparative analysis of a 515-bp region from the male sex- determining locus, Sry, in 22 murine rodents (subfamily Murinae, family Muridae), including representatives from nine species of Mus, and from two additional murine genera--Mastomys and Hylomyscus. Percent sequence divergence was < 0.01% for comparisons between populations within a species and was 0.19%-8.16% for comparisons between species. Our phylogenetic analysis of 12 murine taxa resulted in a single most- parsimonius tree that is highly concordant with phylogenies based on mitochondrial DNA and allozymes. A total evidence tree based on the combined data from Sry, mitochondrial DNA, and allozymes supports (1) the monophyly of the subgenus Mus, (2) its division into a Palearctic group (M. musculus, M. domesticus, M. spicilegus, M. Macedonicus, and M. spretus) and an Oriental group (M. cookii++, M. cervicolor, and M. caroli), and (3) sister-group relationships between M. spicilegus and M. macedonicus and between M. cookii and M. cervicolor. We argue that Y- chromosome DNA sequences represent a valuable new source of characters for phylogenetic inference.      

Le ionophore A23187

The acrosomic status of spermatozoa prepared for IVF has been evaluated by means of immunofluorescence test from Fenichel and Hsi using calcium A 23187 ionophore as inductor of acrosome reaction (AR). The spontaneous AR remains slight, even after 6 hour-incubation in Menezo B2 (6,8+2,7%). The response to ionophore, moderate before (11,2+9%), frankly increases after a 6h-capacitation (28,9+8,3%) in a group of 25 IVF couples (tubal indication, normal semen, positive fertilization). Nevertheless, it remains slight or null in 4 cases of unexplained repeated failure of fertilization. The response to ionophore A 23187 allows to explore the kinetics of capacitation of spermatozoa and their ability to perform AR. Its significance in terms of fecondance remains to be precised.     

Efficient colonization of the endophytes Herbaspirillum huttiense RCA24 and Enterobacter cloacae RCA25 influences the physiological parameters of Oryza sativa L. cv. Baldo rice

Several important bacterial characteristics, such as biological nitrogen fixation, phosphate solubilization, 1-aminocyclopropane-1-carboxylate deaminase activity and production of siderophores and phytohormones, can be assessed as plant growth promotion traits. Our aim was to evaluate the effects of nitrogen fixing and indole-3-acetic acid (IAA) producing endophytes in two Oryza sativa cultivars (Baldo and Vialone Nano). Three bacteria, Herbaspirillum huttiense RCA24, Enterobacter asburiae RCA23 and Staphylococcus sp. 377, producing different IAA levels, were tested for their ability to enhance nifH gene expression and nitrogenase activity in Enterobacter cloacae RCA25. Results showed that H. huttiense RCA24 performed best. Improvement in nitrogen fixation and changes in physiological parameters such as chlorophyll, nitrogen content and shoot dry weight were observed for plants co-inoculated with strains RCA25 and RCA24 in a 10:1 ratio. Based on confocal laser scanning microscopy analysis, strain RCA24 was the best colonizer of the root interior and the only IAA producer located in the same root niche occupied by RCA25 cells. This work shows that the choice of a bio-inoculum having the right composition is one of the key aspects to be considered for the inoculation of a specific host plant cultivar with microbial consortia.     

High Resolution Melting Analysis Targeting hsp70 as a Fast and Efficient Method for the Discrimination of Leishmania Species

Background

Protozoan parasites of the genus Leishmania cause a large spectrum of clinical manifestations known as Leishmaniases. These diseases are increasingly important public health problems in many countries both within and outside endemic regions. Thus, an accurate differential diagnosis is extremely relevant for understanding epidemiological profiles and for the administration of the best therapeutic protocol.

Methods/Principal Findings

Exploring the High Resolution Melting (HRM) dissociation profiles of two amplicons using real time polymerase chain reaction (real-time PCR) targeting heat-shock protein 70 coding gene (hsp70) revealed differences that allowed the discrimination of genomic DNA samples of eight Leishmania species found in the Americas, including Leishmania (Leishmania) infantum chagasi, L. (L.) amazonensis, L. (L.) mexicana, L. (Viannia) lainsoni, L. (V.) braziliensis, L. (V.) guyanensis, L. (V.) naiffi and L. (V.) shawi, and three species found in Eurasia and Africa, including L. (L.) tropica, L. (L.) donovani and L. (L.) major. In addition, we tested DNA samples obtained from standard promastigote culture, naturally infected phlebotomines, experimentally infected mice and clinical human samples to validate the proposed protocol.

Conclusions/Significance

HRM analysis of hsp70 amplicons is a fast and robust strategy that allowed for the detection and discrimination of all Leishmania species responsible for the Leishmaniases in Brazil and Eurasia/Africa with high sensitivity and accuracy. This method could detect less than one parasite per reaction, even in the presence of host DNA.     

Behavioural and chemical mechanisms behind a Mediterranean ant–ant association

1. Interspecific competition among ants is common, and so is competitive exclusion among dominant ant species. In contrast, specific associations between non‐parasitic ant species are rare, especially in the temperate zones. As an exception, the subordinate ant Camponotus lateralis frequently co‐occurs with the dominant Crematogaster scutellaris but rarely with other dominant ants. 2. This association is one of various associations between Camponotus and Crematogaster species across the world. However, the mechanisms behind these co‐occurences are largely unknown. 3. In the present study, we therefore investigated the association of Ca. lateralis and Cr. scutellaris. We studied the spatial association of the nests, interspecific aggression, both species' cuticular hydrocarbon profiles, and their propensity to follow the other species' pheromone trails. 4. Crematogaster scutellaris usually attacked and displaced the generally submissive Ca. lateralis, but was significantly less aggressive at jointly used trails. Camponotus nests were always in close proximity to Crematogaster nests. 5. The cuticular hydrocarbons of both species consisted of alkanes with chain lengths between C21 and C35. The two species had 25 hydrocarbons in common, including mono‐, di‐, and tetramethyl alkanes. Despite this qualitative similarity, however, the quantitative hydrocarbon composition differed between the two species. 6. Camponotus lateralis followed artificial trails containing trail pheromones of Cr. scutellaris, but the latter did not follow Ca. lateralis trail pheromones. Interspecific trail‐following by Camponotus, but not vice versa, has been observed in another Camponotus–Crematogaster association and may be a more general mechanism that facilitates associations between the two ant genera.     

Intra‐floral resource partitioning between endemic and invasive flower visitors: consequences for pollinator effectiveness

1. Sympatric flower visitor species often partition nectar and pollen and thus affect each other's foraging pattern. Consequently, their pollination service may also be influenced by the presence of other flower visiting species. Ants are solely interested in nectar and frequent flower visitors of some plant species but usually provide no pollination service. Obligate flower visitors such as bees depend on both nectar and pollen and are often more effective pollinators. 2. In Hawaii, we studied the complex interactions between flowers of the endemic tree Metrosideros polymorpha (Myrtaceae) and both, endemic and introduced flower‐visiting insects. The former main‐pollinators of M. polymorpha were birds, which, however, became rare. We evaluated the pollinator effectiveness of endemic and invasive bees and whether it is affected by the type of resource collected and the presence of ants on flowers. 3. Ants were dominant nectar‐consumers that mostly depleted the nectar of visited inflorescences. Accordingly, the visitation frequency, duration, and consequently the pollinator effectiveness of nectar‐foraging honeybees (Apis mellifera) strongly decreased on ant‐visited flowers, whereas pollen‐collecting bees remained largely unaffected by ants. Overall, endemic bees (Hylaeus spp.) were ineffective pollinators. 4. The average net effect of ants on pollination of M. polymorpha was neutral, corresponding to a similar fruit set of ant‐visited and ant‐free inflorescences. 5. Our results suggest that invasive social hymenopterans that often have negative impacts on the Hawaiian flora and fauna may occasionally provide neutral (ants) or even beneficial net effects (honeybees), especially in the absence of native birds.     

Sequence and Copy Number Analyses of HEXB Gene in Patients Affected by Sandhoff Disease: Functional Characterization of 9 Novel Sequence Variants

Sandhoff disease (SD) is a lysosomal disorder caused by mutations in the HEXB gene. To date, 43 mutations of HEXB have been described, including 3 large deletions. Here, we have characterized 14 unrelated SD patients and developed a Multiplex Ligation-dependent Probe Amplification (MLPA) assay to investigate the presence of large HEXB deletions. Overall, we identified 16 alleles, 9 of which were novel, including 4 sequence variation leading to aminoacid changes [c.626C>T (p.T209I), c.634C>A (p.H212N), c.926G>T (p.C309F), c.1451G>A (p.G484E)] 3 intronic mutations (c.1082+5G>A, c.1242+1G>A, c.1169+5G>A), 1 nonsense mutation c.146C>A (p.S49X) and 1 small in-frame deletion c.1260_1265delAGTTGA (p.V421_E422del). Using the new MLPA assay, 2 previously described deletions were identified. In vitro expression studies showed that proteins bearing aminoacid changes p.T209I and p.G484E presented a very low or absent activity, while proteins bearing the p.H212N and p.C309F changes retained a significant residual activity. The detrimental effect of the 3 novel intronic mutations on the HEXB mRNA processing was demonstrated using a minigene assay. Unprecedentedly, minigene studies revealed the presence of a novel alternative spliced HEXB mRNA variant also present in normal cells. In conclusion, we provided new insights into the molecular basis of SD and validated an MLPA assay for detecting large HEXB deletions.