Dimethylsulfone as a growth substrate for novel methylotrophic species of Hyphomicrobium and Arthrobacter

Dimethylsulfone is a major product of the chemical oxidation in the atmosphere of the principal biogenic sulfur gas, dimethylsulfide, but no studies have been reported on the mechanisms for its microbiological degradation. Three novel strains of bacteria have been isolated from enrichment cultures provided with dimethylsulfone as the only carbon and energy substrate. These are novel facultatively methylotrophic species of Hyphonmicrobium and Arthobacter, capable of growth on a range of one-carbon substrates. Cell-free extracts contained activities of enzymes necessary for a reductive/oxidative pathway for dimethylsulfone degradation: membrane-bound-dimethylsulfone and dimethylsulfoxide reductases, dimethylsulfide monooxygenase, and methanethiol oxidase. Enzymatic evidence is also presented for the subsequent oxidation of formaldehyde by formaldehyde and formate dehydrogenases in the Hyphomicrobium strain and by a dissimilatory ribulose monophosphate cycle in the Arthrobacter strains. The strains also grew on dimethylsulfoxide and dimethylsulfide, and dimethylsulfide-grown bacteria oxidized dimethylsulfide and dimethylsulfoxide but not dimethylsulfone. Formaldehyde assimilation was effected in the Hyphomicrobium strain by the serine pathway, but enzymes of the ribulose monophosphate cycle for formaldehyde assimilation were present in the Arthrobacter strains grown on dimethylsulfone. In contrast, one of the Arthrobacter strains was shown to switch to the serine pathway during growth on methanol. Growth yields on dimethylsulfone and formaldehyde were consistent with the occurrence of the serine pathway in Hyphomicrobium strain S1 and the ribulose monophosphate cycle in Arthrobacter strain TGA, and with the proposed reductive pathway for dimethylsulfone degradation in both.     

Aberrant chloroplasts in transgenic rice plants expressing a high level of maize NADP-dependent malic enzyme

 NADP-dependent malic enzyme (NADP-ME) is a major decarboxylating enzyme in NADP-ME-type C₄ species such as maize and Flaveria. In this study, chloroplastic NADP-ME was transferred to rice (Oryza sativa L.) using a chimeric gene composed of maize NADP-ME cDNA under the control of rice light-harvesting chlorophyll-a/b-binding protein (Cab) promoter. There was a 20- to 70-fold increase in the NADP-ME activity in leaves of transgenic rice compared to that in wild-type rice plants. Immunocytochemical studies by electron microscopy showed that maize NADP-ME was mostly localized in chloroplasts in transgenic rice plants, and that the chloroplasts were agranal without thylakoid stacking. Chlorophyll content and photosystem II activity were inversely correlated with the level of NADP-ME activity. These results suggest that aberrant chloroplasts in transgenic plants may be caused by excessive NADP-ME activity. Based on these results and the known fact that only bundle sheath cells of NADP-ME species, among all three C₄ subgroups, have agranal chloroplasts, we postulate that a high level of chloroplastic NADP-ME activity could strongly affect the development of chloroplasts. Received: 27 January 1999 / Accepted: 20 January 2000     

Over-expression of a tobacco homeobox gene, NTH15 , decreases the expression of a gibberellin biosynthetic gene encoding GA 20-oxidase

Ectopic expression of the homeobox gene, NTH15 ( Nicotiana tabacum homeobox 15) in transgenic tobacco leads to abnormal leaf and flower morphology, accompanied by a decrease in the content of the active gibberellin, GA₁. Quantitative analysis of intermediates in the GA biosynthetic pathway revealed that the step from GA₁₉ to GA₂₀ was blocked in transgenic tobacco plants overexpressing NTH15 . To investigate the relationship between the expression of NTH15 and genes involved in GA biosynthesis, we isolated three cDNA clones from tobacco encoding two types of GA 20-oxidase and a 3β-hydroxylase. RNA gel blot analysis revealed that the expression of one gene ( Ntc12 , encoding GA 20-oxidase), which in wild-type tobacco plants was abundantly expressed in leaves, was strongly suppressed in the transformants. The expression level of Ntc12 decreased with increasing severity of phenotype of transgenic tobacco leaves. The abnormal leaf morphology was largely overcome by treatment with GA₂₀ or GA₁ but not by GA₁₉. These data strongly suggest that overexpression of NTH15 inhibits the expression of Ntc12 , resulting in reduced levels of active GA and abnormal leaf morphology in transgenic tobacco plants. In situ hybridization in wild-type tobacco revealed that expression of Ntc12 occurred mainly in the rib meristem, cells surrounding the procambium and in leaf primordia. Expression was not seen in the tunica, corpus and procambium, tissues in which NTH15 was predominantly expressed. The contrasting expression patterns of these genes may reflect their antagonistic functions in the formation of lateral organs from the shoot apical meristem.     

Aggregation as a cost-reducing strategy for lycaenid larvae

If a mutualistic relationship entails providing services ata cost, selection will favor individuals that maximize the netbenefits of the interaction and minimize the costs. Larvae ofmany species of lycaenid butterflies secrete nutritious foodrewards to attending ants and, in return, receive protectionagainst predators and parasitoids. Because ants typically recruitmore workers to larger resources, by forming groups the larvaemay ensure more reliable access to ants and thereby gain betterprotection. A further consequence of aggregating should be achange of the cost-benefit relationship for individual larvae.The larger the group, the smaller a single larva's influencewill be on total ant density, which could lead to a smallerinvestment in secretion, thus reducing the per capita cost ofcooperation. In this study, die influence of ant attendance,group size, and companion quality on larval investment was investigated.The interaction between the obligately ant-dependent lycaenid,Jalmanus evagoras, and its attendant Iridomyrmax ants was manipulatedand the effect on larval secretion measured. As the level ofant attendance increased, the delivery of food rewards increased,bodi for solitary and for aggregated larvae. When aggregated,larvae provided less food rewards to ants dun when solitary,and secretion rate decreased with increasing group size. Furthermore,larvae had lower secretion rates when paired with a bigger,more attractive larva than when paired with a smaller one. Theconsiderable reduction in secretion rates for larvae in groupssuggests that gaining protection at a lower secretion cost couldbe one factor that promotes aggregation in myrmecophilous lycaenids.     

RESOLVING EVOLUTIONARY RELATIONSHIPS AMONG THE BROWN ALGAE USING CHLOROPLAST AND NUCLEAR GENES1

The brown algae are one of the largest and most important groups of primary producers in benthic coastal marine environments. Despite their biological importance, consensus regarding their taxonomic or evolutionary relationships remains elusive. Our goal was to produce a taxon‐rich two‐gene (rbcL and LSU rDNA) phylogeny. Key species were sequenced to represent each order and family in the analyses across all 19 orders and ～40 families, including selected outgroups Schizocladiophyceae and Xanthophyceae. Our results are in sharp contrast to traditional phylogenetic concepts; the Ectocarpales are not an early diverging clade, nor do the Fucales diverge early from other brown algae. Rather, Choristocarpus is sister to the remaining brown algae. Other groups traditionally considered to have primitive features are actually recently diverged lineages, turning traditional phylogenetic concepts upside down. Additionally, our results allow for the assessment, in the broadest context, of many of the historical and more recent taxonomic changes, resulting in several emended groups along with proposals for two new orders (Onslowiales, Nemodermatales) and one new family (Phaeosiphoniellaceae).     

AUDIT,AUDIT-C,and AUDIT-3: Drinking Patterns and Screening for Harmful,Hazardous and Dependent Drinking in Katutura,Namibia

Objectives

To describe alcohol drinking patterns among participants in Katutura, Namibia, and to evaluate brief versions of the AUDIT against the full AUDIT to determine their effectiveness in detecting harmful drinking.

Methods

A cross-sectional survey was conducted in four constituencies and 639 participants, 18 years or older, completed a sociodemographic survey and the AUDIT. The effectiveness of the AUDIT-C (first three questions) and the AUDIT-3 (third question) was compared to the full AUDIT.

Results

Approximately 40% were identified as harmful, hazardous or likely dependent drinkers, with men having a higher likelihood than women (57.2% vs. 31.0%, p<.0001). Approximately 32% reported making and/or selling alcohol from home. The AUDIT-C performed best at a cutoff ≥ 3, better in men (sensitivity: 99.3%, specificity: 77.8%) than women (sensitivity: 91.7%, specificity: 77.4%). The AUDIT-3 performed poorly (maximum sensitivity: < 90%, maximum specificity: <51%). According to AUROC, the AUDIT-C performed better than the AUDIT-3.

Conclusions

A large proportion of participants met criteria for alcohol misuse, indicating a need for screening and referral for further evaluation and intervention. The AUDIT-C was almost as effective as the full AUDIT and may be easier to implement in clinical settings as a routine screening tool in resource-limited settings because of its brevity.     

Factors that Influence the Way Communities Respond to Proposals for Major Changes to Local Emergency Services: A Qualitative Study

Objective

According to policy commentators, decisions about how best to organise care involve trade-offs between factors relating to care quality, workforce, cost, and patient access. In England, proposed changes such as Emergency Department closures often face public opposition. This study examined the way communities respond to plans aimed at reorganising emergency services, including the trade-offs inherent in such decisions.

Design

Cross-sectional study involving in-depth interviews. Participants selected their priorities for emergency care, including aspects they might be prepared to have ‘less’ of (e.g. rapid access) if it meant having ‘more’ of another (e.g. consultant-delivered care). A thematic analysis was carried out, combining inductive and deductive approaches, drawing on theories about risk perception.

Setting

Two urban areas of England; one where changes to emergency services were under consideration (‘Greenville’), and one where they were not (‘Hilltown’).

Participants

28 participants in total. Greenville interviewees included more common emergency service users - parents of young children (n=5) and older people (n=6) - plus patient representatives and individuals campaigning against service closures (n=9). Hilltown interviewees (n=8) received outpatient care for Chronic Obstructive Pulmonary Disease, an important cause of emergency admission.

Results

Most participants, in both areas, were not willing to accommodate the trade-offs involved in consolidating emergency services, principally because of the belief that timely access is associated with better outcomes. Participants did not consider the proposed improvements as gains worth having; interviewees believed care quality would be adversely impact, partly because increased patient numbers would place staff under greater pressure and result in longer waiting times.

Conclusions

Visible clinical leadership and detailed explanation of the case for change were insufficient to overcome opposition to the reconfiguration in Greenville, challenging the assumption that communities can be persuaded by evidence. Commissioners should make explicit credible plans to accommodate changes in patient flows, as well as clarifying the roles played by key staff groups.     

Arabinogalactan biosynthesis: Implication of AtGALT29A enzyme activity regulated by phosphorylation and co-localized enzymes for nucleotide sugar metabolism in the compartments outside of the Golgi apparatus

Arabinogalactan proteins are abundant cell surface proteoglycans in plants and are implicated to act as developmental markers during plant growth. We previously reported that AtGALT31A, AtGALT29A, and AtGLCAT14A-C, which are involved in the biosynthesis of arabinogalactan proteins, localize not only to the Golgi cisternae but also to smaller compartments, which may be a part of the unconventional protein secretory pathway in plants. In Poulsen et al.,¹ we have demonstrated increased targeting of AtGALT29A to small compartments when Y144 is substituted with another amino acid, and we implicated a role for Y144 in the subcellular targeting of AtGALT29A. In this paper, we are presenting another aspect of Y144 substitution in AtGALT29A; namely, Y144A construct demonstrated a 2.5-fold increase while Y144E construct demonstrated a 2-fold decrease in the galactosyltransferase activity of AtGALT29A. Therefore, the electrostatic status of Y144, which is regulated by an unknown kinase/phosphatase system, may regulate AtGALT29A enzyme activity. Moreover, we have identified additional proteins, apyrase 3 (APY3; At1g14240) and UDP-glucuronate epimerases 1 and 6 (GAE1, At4g30440; GAE6, At3g23820), from Arabidopsis thaliana that co-localize with AtGALT31A in the small compartments when expressed transiently in Nicotiana benthamiana. These proteins may play roles in nucleotide sugar metabolism in the small compartments together with arabinogalactan glycosyltransferases.