THE DISINFECTANT PROPERTIES OF QUATERNARY AMMONIUM COMPOUNDS AND SODIUM HYPOCHLORITE: A COMPARISON OF RESULTS USING DIFFERENT TEST METHODS

SUMMARY: On exposing a strain of Bacterium coli 28.D.10 in a surface film at atmospheric temperature to atmospheres of different moisture contents, it was found that for relative humidities between 100 and 66% the numbers of survivors decreased with decreasing humidity. There was also some evidence of a slight increase in survivors for a decrease in relative humidity from 43 to 0%.
The percentage of survivors of Bact. coli after exposure to quaternary ammonium disinfectants also decreased with relative humidity between 100 and 66% but no significant differences were found for changes in relative humidity below 66%. The numbers of survivors of a culture of Staphylococcus aureus were the same after storage at a relative humidity of 43% as at 100%; drying did not appear to affect the sensitivity of Staph. aureus to quaternary ammonium compounds. Tests of the effect of storage time in a saturated atmosphere gave results which were not entirely consistent, but where differences were observed, there was a lower percentage of survivors for freshly inoculated films than for films which had been stored for 3 hr, presumably because a fresh film was more easily removed to the disinfectant.
When either Bact. coli or Staph. aureus was exposed to a disinfectant, the percentage of survivors was higher when the organisms were in a surface film than when they were inoculated directly into the disinfectant. Agitation during exposure reduced the numbers of survivors from a surface film. Neither the glass nor the metal coming in contact with the disinfectants affected the level of survivors.
Under the conditions of testing, sodium hypochlorite was a more effective disinfectant than the quaternary ammonium compounds used.     

Generic interrelationships within the Spionidae (Annelida: Polychaeta)

The phylogenetic relationships of spionid genera are estimated from parsimony analyses of morphological characters, with Trochochaetidae, Poecilochaetidae and Uncispionidae as outgroups. A first analysis of currendy recognised genera proved inconclusive and even exclusion of six of the most polymorphic genera resulted in 13 305 equally parsimonious trees and a fully collapsed consensus tree. A second analysis using only the type species of each genus, yielded four equally parsimonious trees; reduced to two after successive weighting. The topologies of these two trees indicated division of the family into four main groups: (1) Aonidella and Xandaros; (2) Prionospio (sensu fato)-complex, Laonice, Spiophanes and Aonides; (3) a large assemblage of genera, including Polydora-{senm late), Scolelepis, Malacoceros and Spio; (4) Atherospio, Pseudatherospio and Pygospiopsis. Earlier literature classifications of the group are evaluated and compared with die new results.     

Dry nitrogen deposition estimates over a forest experiencing free air CO2 enrichment

The quantification of atmospheric additions of nitrogen (N) to an ecosystem is often desirable, but difficult for many locations including many ecological manipulation experiments. Ideal methodologies for the complete and chemically speciated quantification of dry N deposition (e.g. tunable diode laser absorption spectrometer, thermal‐dissociation laser‐induced fluorescence) are expensive, technologically challenging to maintain, and rarely colocated with important global change manipulation experiments. Here we present an alternative method for obtaining an approximation of total N deposition using short‐term eddy flux and concentration measurements, annual regional concentration estimates, and modeling for the Duke Experimental Forest. The motivation for generating estimates for this location was to inform the long‐term elevated CO₂ experiment conducted at Duke Forest. We estimated the total annual atmospheric N deposition to the forest to be 13.7 kg N ha^?1. Of this total, ～58% was in dry‐deposited forms. Surprisingly, and contrary to some previous predictions, nitric acid (HNO₃) was not the dominant portion of the total dry‐deposited N, implying strongly that other forms of gaseous N like organic peroxy and alkyl nitrate compounds are a significant portion of the total flux. Furthermore, this study sheds light on the completeness of the estimates derived from Clean Air Status and Trends Network (CASTNet) and other dry deposition networks. CASTNet does not measure organic forms of dry deposition. In fact, CASTNet only quantifies HNO₃ in the gas phase and may significantly underestimate total N deposition in many environments.     

Effect of fire regime on plant abundance in a tropical eucalypt savanna of north‐eastern Australia

Abstract Changes in plant abundance within a eucalypt savanna of north‐eastern Australia were studied using a manipulative fire experiment. Three fire regimes were compared between 1997 and 2001: (i) control, savanna burnt in the mid‐dry season (July) 1997 only; (ii) early burnt, savanna burnt in the mid‐dry season 1997 and early dry season (May) 1999; and (iii) late burnt, savanna burnt in the mid‐dry season 1997 and late dry season (October) 1999. Five annual surveys of permanent plots detected stability in the abundance of most species, irrespective of fire regime. However, a significant increase in the abundance of several subshrubs, ephemeral and twining perennial forbs, and grasses occurred in the first year after fire, particularly after late dry season fires. The abundance of these species declined toward prefire levels in the second year after fire. The dominant grass Heteropogon triticeus significantly declined in abundance with fire intervals of 4 years. The density of trees (>2 m tall) significantly increased in the absence of fire for 4 years, because of the growth of saplings; and the basal area of the dominant tree Corymbia clarksoniana significantly increased over the 5‐year study, irrespective of fire regime. Conservation management of these savannas will need to balance the role of regular fires in maintaining the diversity of herbaceous species with the requirement of fire intervals of at least 4‐years for allowing the growth of saplings >2 m in height. Whereas late dry season fires may cause some tree mortality, the use of occasional late fires may help maintain sustainable populations of many grasses and forbs.     

Phenotypic plasticity of a cooperative behaviour in bacteria

There is strong evidence that natural selection can favour phenotypic plasticity as a mechanism to maximize fitness in animals. Here, we aim to investigate phenotypic plasticity of a cooperative trait in bacteria – the production of an iron‐scavenging molecule (pyoverdin) by Pseudomonas aeruginosa. Pyoverdin production is metabolically costly to the individual cell, but provides a benefit to the local group and can potentially be exploited by nonpyoverdin‐producing cheats. Here, we subject bacteria to changes in the social environment in media with different iron availabilities and test whether cells can adjust pyoverdin production in response to these changes. We found that pyoverdin production per cell significantly decreased at higher cell densities and increased in the presence of cheats. This phenotypic plasticity significantly influenced the costs and benefits of cooperation. Specifically, the investment of resources into pyoverdin production was reduced in iron‐rich environments and at high cell densities, but increased under iron limitation, and when pyoverdin was exploited by cheats. Our study demonstrates that phenotypic plasticity in a cooperative trait as a response to changes in the environment occurs in even the simplest of organisms, a bacterium.     

Habitat preferences of the noisy miner (Manorina melanocephala) – a propensity for prime real estate?

This study investigated habitat characteristics that have been postulated to influence the occurrence of noisy miners (Manorina melanocephala Family Meliphagidae). It builds on an earlier study that identified corners along remnant edges as important predictors of the presence of noisy miners in large blocks of remnant vegetation (>300 ha). Six habitat characteristics were recorded at 39 corner sites within the box‐ironbark region of Victoria. We failed to detect any significant effect of the density of understorey vegetation on the likelihood of noisy miners occupying a site, but this might have been an artefact of prolonged drought conditions. The most powerful predictors of the presence of noisy miners at remnant corners were found to be soil type and the proportion of canopy trees at a site that were yellow gum (Eucalyptus leucoxylon), with noisy miners being associated with deeper, more fertile soils and higher proportions of yellow gums present. As yellow gum is a prolific and reliable nectar producer, the inherent productivity of a site might be more important in determining the attractiveness of a site to noisy miners than structural attributes like the presence or absence of an understorey. Noisy miners are sedentary colonial birds that occupy year‐round territories, often at high densities. Sites capable of supporting such high density occupation year‐round might be limited to the most productive sites within the landscape. This productivity hypothesis has potentially profound implications for other woodland avifauna, as noisy miners might be excluding other woodland birds from some of the most fertile components of the landscape; components that are already rare in the box‐ironbark region due preferential clearing for agriculture at the time of settlement.     

Contributions of the effector gene hopQ1-1 to differences in host range between Pseudomonas syringae pv. phaseolicola and P. syringae pv. tabaci

To study the role of type III-secreted effectors in the host adaptation of the tobacco ( Nicotiana sp.) pathogen Pseudomonas syringae pv. tabaci , a selection of seven strains was first characterized by multilocus sequence typing (MLST) to determine their phylogenetic affinity. MLST revealed that all strains represented a tight phylogenetic group and that the most closely related strain with a completely sequenced genome was the bean ( Phaseolus vulgaris ) pathogen P. syringae pv. phaseolicola 1448A. Using primers designed to 21 P. syringae pv. phaseolicola 1448A effector genes, it was determined that P. syringae pv. phaseolicola 1448A shared at least 10 effectors with all tested P. syringae pv. tabaci strains. Six of the 11 effectors that failed to amplify from P. syringae pv. tabaci strains were individually expressed in one P. syringae pv. tabaci strain. Although five effectors had no effect on phenotype, growth in planta and disease severity of the transgenic P. syringae pv. tabaci expressing hopQ1-1 _Pph1448A were significantly increased in bean, but reduced in tobacco. We conclude that hopQ1-1 has been retained in P. syringae pv. phaseolicola 1448A, as this effector suppresses immunity in bean, whereas hopQ1-1 is missing from P. syringae pv. tabaci strains because it triggers defences in Nicotiana spp. This provides evidence that fine-tuning effector repertoires during host adaptation lead to a concomitant reduction in virulence in non-host species.     

Colour plasticity and background matching in a threespine stickleback species pair

Examining differences in colour plasticity between closely‐related species in relation to the heterogeneity of background colours found in their respective habitats may offer important insight into how cryptic colour change evolves in natural populations. In the present study, we examined whether nonbreeding dorsal body coloration has diverged between sympatric species of stickleback along with changes in habitat‐specific background colours. The small, limnetic species primarily occupies the pelagic zone and the large, benthic species inhabits the littoral zone. We placed benthic and limnetic sticklebacks against extremes of habitat background colours and measured their degree of background matching and colour plasticity. Benthics matched the littoral background colour more closely than did the limnetics, although there was no difference between species in their resemblance to the pelagic background colour. Benthics were able to resemble both background colours by exhibiting greater directional colour plasticity in their dorsal body coloration than limnetics, which may be an adaptive response to the greater spectral heterogeneity of the littoral zone. The present study highlights how habitat‐specific spectral characteristics may shape cryptic coloration differences between stickleback species. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102 , 902–914.     

Inter- and intrasexual dimorphism in the diving beetle Hydroporus memnonius Nicolai (Coleoptera: Dytiscidae)

Sexual conflict can drive rapid intersexual arms races, and lead to pronounced sexual dimorphism. Such dimorphism is frequent in diving beetles, where males typically possess expanded front and middle tarsi, supplied with adhesive setae to grasp females during mating, and females often have rough dorsal surfaces which hinder male attachment. In a number of species, females are dimorphic, being either smooth and male-like, or heavily sculptured dorsally. Smooth and sculptured females often have distinct biogeographies, and may be expected to be associated with specific counter-adaptations in males. The European diving beetle, Hydroporus memnonius Nicolai, includes a smooth male-like female, and a matt morph, var. castaneus Aubé, which are largely allopatric in distribution. We show that the two morphs differ in the density and intensity of their surface microreticulation, and that matt females are associated with morphologically distinct males, which have developed specific countermeasures on their tarsi, including a greater number of large adhesive setae, individually larger in area. Such males are expected to be more successful in pairing with both matt and shining females, and it is suggested that a process of population replacement, partly driven by sexual interactions, may occur where the two forms overlap in range.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 94 , 685–697.