ECOTYPIC VARIATION IN PHYLLOPHORA PSEUDOCERANOIDES (RHODOPHYTA) ENSURES WINTER REPRODUCTION THROUGHOUT ITS GEOGRAPHIC RANGE1

Responses to temperature and daylength were determined in laboratory culture for isolates of the red alga Phyllophora pseudoceranoides (Gmelin) Newroth et A.R.A. Taylor from Nova Scotia, Iceland, Roscoff (France), and Helgoland (Germany). All isolates grew from 3° to 25° C and survived from -2° or 0° C to 27° C but not 30° C. Reproductive requirements differed between life history phases and isolates. Isolates from Helgoland and Roscoff formed sporangial sori at 3°-20° C, tetraspores at 3°-12° C, and procarps at 10°-20° C, irrespective of daylength. Spermatangia developed at 10°-23° C but only in long days. As the other European isolates, the isolate from Iceland formed tetrasporangia at 3°-12° C, but it had an additional requirement for short days. The Nova Scotian isolate formed sori at 10°-20° C and sporulated at 10°-18° C. When grown plants were transferred from noninductive to inductive conditions, sori were formed after 4 months and tetraspores developed and were shed (1-)3 months later. Procarps formed 1(-3) months after transfer. The phenology of P. pseudoceranoides was studied at Helgoland and Roscoff, where similar seasonal patterns were observed. Plants were perennial, forming new blades from October to June, which degenerated between August and February. In June, reproductive structures (sori, spermatangia, and procarps) started to appear on the new blades. From October to April, mature cystocarps were found. Mature tetrasporangia were observed only in February. The life history of P. pseudoceranoides is regulated by temperature and daylength. Differential effects on the different life history phases all serve to confine the production of spores (both carpospores and tetraspores) to the winter season. Differences in response between isolates from different geographic regions bring about the same effect: spores are shed only in winter. The nature of the geographic boundaries of P. pseudoceranoides is discussed.     

TEMPERATURE RESPONSES AND EVOLUTION OF THERMAL TRAITS IN CLADOPHOROPSIS MEMBRANACEA (SIPHONOCLADALES,CHLOROPHYTA)1

Temperature tolerances and relative growth rates were determined for different isolates of the tropical to warm temperate seaweed species Cladophoropsis membranacea (C. Agardh) Boergesen (Siphonodadales, Chlorophyta) and some related taxa. Most isolates of C membranacea survived undamaged at 18° C for at least 8 weeks. Lower temperatures (5°–15°C) were tolerated for shorter periods of time but caused damage to cells. All isolates survived temperatures up to 34° C, whereas isolates from the eastern Mediterranean and Red Sea survived higher temperatures up to 36°C. Growth occurred between 18° and 32° C, but an isolate from the Red Sea had an extended growth range, reaching its maximum at 35°C. Struvea anastomosans (Harvey) Piccone & Grunow, Cladophoropsis sundanensis Reinbold, and an isolate of C. membranacea from Hawaii were slightly less cold- tolerant, with damage occurring at 18°C. Upper survival temperatures were between 32° and 36° C in these taxa. Temperature response data were mapped onto a phylogenetic tree. Tolerance for low temperatures appears to be a derived character state that supports the hypothesis that C. membranacea originated from a strictly tropical ancestor. Isolates from the Canary Islands, which is near the northern limit of distribution, are ill adapted to local temperature regimes. Isolates from the eastern Mediterranean and Red Sea show some adaptation to local temperature stress. They are isolated from those in the eastern Atlantic by a thermal barrier at the entrance of the Mediterranean.     

Compartmentation of Alternative Oxidase in Plant Mitochondria

Capacity of alternative pathway mediated, CN-resistant respirationwas measured in mitochondria isolated from three plant species:Iris bulbs, potato tuber callus and Petunia cells, grown insuspension culture. Succinate, NADH or a combination of succinateand NADH were used as respiratory substrates. In all three plantspecies electrons from exogenous NADH appeared to have no accessto the alternative pathway connected with succinate mediatedrespiration and vice versa. Therefore, besides a (functional)compartmentation of Q-pools a compartmentation of alternativepathways in plant mitochondria is proposed as well. (Received October 19, 1985; Accepted January 29, 1986)     

Oxygen-induced cytogenetic instability in normal human lymphocytes

Summary Chromosomal aberrations were scored in normal human lymphocytes cultured for 3 to 7 days at 20, 40, 50, and 60% oxygen. Compared to normoxic cultures (20% O₂), in hyperoxic cultures (40% to 60% O₂) the frequency of aberrant cells was significantly increased, especially at the longer incubation times. The increase was mainly due to chromatid-type damage: chromatid gaps, breaks, and interchanges. In addition, long-term hyperoxic cultures had a remarkably high incidence of endoreduplications, up to 7.4%. It appears that prolonged hyperoxic incubation induces a pattern of cytogenetic abnormalities in normal human lymphocytes similar to that present spontaneously in 3-day normoxic cultures from patients with Fanconi anemia.     

The Widespread Presence of a Multidrug-Resistant Escherichia coli ST131 Clade among Community-Associated and Hospitalized Patients

Background & Aims

The extent of entry of multidrug-resistant Escherichia coli from the community into the hospital and subsequent clonal spread amongst patients is unclear. To investigate the extent and direction of clonal spread of these bacteria within a large teaching hospital, we prospectively genotyped multidrug-resistant E. coli obtained from community- and hospital associated patient groups and compared the distribution of diverse genetic markers.

Methods

A total of 222 E. coli, classified as multi-drug resistant according to national guidelines, were retrieved from both screening (n = 184) and non-screening clinical cultures (n = 38) from outpatients and patients hospitalized for various periods. All isolates were routinely genotyped using an amplified fragment length polymorphism (AFLP) assay and real-time PCR for CTX-M genes. Multi-locus sequence typing was additionally performed to confirm clusters. Based on demographics, patients were categorized into two groups: patients that were not hospitalized or less than 72 hours at time of strain isolation (group I) and patients that were hospitalized for at least 72 hours (group II).

Results

Genotyping showed that most multi-drug resistant E. coli either had unique AFLP profiles or grouped in small clusters of maximally 8 isolates. We identified one large ST131 clade comprising 31% of all isolates, containing several AFLP clusters with similar profiles. Although different AFLP clusters were found in the two patient groups, overall genetic heterogeneity was similar (35% vs 28% of isolates containing unique AFLP profiles, respectively). In addition, similar distributions of CTX-M groups, including CTX-M 15 (40% and 44% of isolates in group I and II, respectively) and ST131 (32% and 30% of isolates, respectively) were found.

Conclusion

We conclude that multi-drug resistant E. coli from the CTX-M 15 associated lineage ST131 are widespread amongst both community- and hospital associated patient groups, with similar genetic diversity and similar distributions of genetic markers.     

Photoperiodic history affects the critical daylength of the short-day plant Acrosymphyton purpuriferum (Rhodophyta)

The crustose tetrasporophyte of the red alga Acrosymphyton purpuriferum is a qualitative short-day plant in the formation of its tetrasporangia. The critical daylength for the response was determined in plants precultured in various long-day regimes [20:4, 18:6, 16:8 and 14:10 (L:D, h)]. There was a strong influence of photoperiodic history. The sharper the decrease in daylength the stronger and faster the plants responded. The critical daylength (daylength inducing 50% response) increased from 9·5 h for plants precultured in 14 h days to 12·5 h for plants precultured in 20 h days. Acrosymphyton thus responds to a change in daylength, rather than to a fixed critical value. This is of adaptive significance in synchronising the onset of reproduction throughout its broad depth range in the subtidal region.     

A Protein Prioritization Approach Tailored for the FA/BRCA Pathway

Fanconi anemia (FA) is a heterogeneous recessive disorder associated with a markedly elevated risk to develop cancer. To date sixteen FA genes have been identified, three of which predispose heterozygous mutation carriers to breast cancer. The FA proteins work together in a genome maintenance pathway, the so-called FA/BRCA pathway which is important during the S phase of the cell cycle. Since not all FA patients can be linked to (one of) the sixteen known complementation groups, new FA genes remain to be identified. In addition the complex FA network remains to be further unravelled. One of the FA genes, FANCI, has been identified via a combination of bioinformatic techniques exploiting FA protein properties and genetic linkage. The aim of this study was to develop a prioritization approach for proteins of the entire human proteome that potentially interact with the FA/BRCA pathway or are novel candidate FA genes. To this end, we combined the original bioinformatics approach based on the properties of the first thirteen FA proteins identified with publicly available tools for protein-protein interactions, literature mining (Nermal) and a protein function prediction tool (FuncNet). Importantly, the three newest FA proteins FANCO/RAD51C, FANCP/SLX4, and XRCC2 displayed scores in the range of the already known FA proteins. Likewise, a prime candidate FA gene based on next generation sequencing and having a very low score was subsequently disproven by functional studies for the FA phenotype. Furthermore, the approach strongly enriches for GO terms such as DNA repair, response to DNA damage stimulus, and cell cycle-regulated genes. Additionally, overlaying the top 150 with a haploinsufficiency probability score, renders the approach more tailored for identifying breast cancer related genes. This approach may be useful for prioritization of putative novel FA or breast cancer genes from next generation sequencing efforts.     

Localization of DNA probes with tight linkage to the cystic fibrosis locus by in situ hybridization using fibroblasts with a 7q22 deletion

Summary Five DNA probes known to originate from the region 7q22-q31 were sublocalized by in situ hybridization to metaphase preparations of fibroblasts having besides a normal chromosome 7, a homologue 7 with an apparent interstitial deletion of a large part of band q22. A flow cytometric chromosome analysis confirmed a loss of material from one of the homologues of chromosome 7. Four of the probes, B79a, 7C22,metH, and pJ3.11, have been shown to be closely linked to the cystic fibrosis (CF) locus. We localized probes B79a and 7C22 to the part of 7q22 involved in the deletion, whereasmetH and pJ3.11 could be assigned to band 7q31. Probe pJu28, for which polymorphisms have not yet been described, also appeared to derive from the latter band. Since pJ3.11 andmetH are most tightly linked to the CF locus, this disease locus is indirectly assigned to 7q31. A comparison of our findings with linkage data suggests a discrepancy between genetic and physical distances in the region 7q22-q31.     

SEASONAL CHANGES IN SIZE STRUCTURE OF SARGASSUM AND TURBINARIA POPULATIONS (PHAEOPHYCEAE) ON TROPICAL REEF FLATS IN THE SOUTHERN RED SEA1

Seasonal variation in density, thallus length and biomass, population size structure, and allometric length‐biomass relationships was investigated in populations of Sargassum ilicifolium (Turner) C. Agardh, Sargassum subrepandum (Forssk.) C. Agardh, and Turbinaria triquetra (J. Agardh) Kütz. (Phaeophyceae) on shallow reef flats in the southern Red Sea. Thallus length and biomass varied strongly with season, with the highest values occurring in the cooler months. Thallus densities showed no significant temporal variation. Log‐total biomass versus log‐density relationships were positive throughout the growth season without any decrease in the slope of the relationship. In two populations, biomass‐density combinations approached the interspecific biomass‐density line, but the massive annual shedding of modules occurred before self‐thinning would set in. Allometric length‐biomass relationships varied with season in all populations and were associated with seasonal module initiation, growth, and shedding. Evidence of a strong asymmetric competition was found in two high‐density populations. These populations showed a predominance of small thalli during peak development, asymmetrical Lorenz curves, increasing Gini coefficients, and increasing thallus length relative to biomass during the main growth phase. In two other less crowded populations, small thalli were absent during peak development, Lorenz curves were symmetrical, and Gini coefficients decreased during the main growth phase. In these populations, size equalization appears to be due to responses at the modular level rather than size‐dependent mortality. We conclude that changes in size structure in this highly seasonal environment are determined by module dynamics, modified by asymmetric competition in some populations, with a minor role of recruitment and no regulatory effect of self‐thinning.     

A Nonsense Mutation in PDE6H Causes Autosomal-Recessive Incomplete Achromatopsia

Achromatopsia (ACHM) is an autosomal-recessive retinal dystrophy characterized by color blindness, photophobia, nystagmus, and severely reduced visual acuity. Its prevalence has been estimated to about 1 in 30,000 individuals. Four genes, GNAT2, PDE6C, CNGA3, and CNGB3, have been implicated in ACHM, and all encode functional components of the phototransduction cascade in cone photoreceptors. Applying a functional-candidate-gene approach that focused on screening additional genes involved in this process in a cohort of 611 index cases with ACHM or other cone photoreceptor disorders, we detected a homozygous single base change (c.35C>G) resulting in a nonsense mutation (p.Ser12^∗) in PDE6H, encoding the inhibitory γ subunit of the cone photoreceptor cyclic guanosine monophosphate phosphodiesterase. The c.35C>G mutation was present in three individuals from two independent families with a clinical diagnosis of incomplete ACHM and preserved short-wavelength-sensitive cone function. Moreover, we show through immunohistochemical colocalization studies in mouse retina that Pde6h is evenly present in all retinal cone photoreceptors, a fact that had been under debate in the past. These findings add PDE6H to the set of genes involved in autosomal-recessive cone disorders and demonstrate the importance of the inhibitory γ subunit in cone phototransduction.