Role of ‘<Emphasis Type="Italic">Candidatus</Emphasis> Liberibacter solanacearum’ and <Emphasis Type="Italic">Bactericera cockerelli</Emphasis> Haplotypes in Zebra Chip Incidence and Symptom Severity

Two haplotypes of the pathogen, ‘Candidatus Liberibacter solanacearum,’ (Lso) and four haplotypes of the insect vector, Bactericera cockerelli, are associated with zebra chip disease of potato. Whether disease severity or incidence is influenced by pathogen or insect haplotype is poorly understood. The role of Lso ‘A’ and ‘B,’ transmitted by three haplotypes of B. cockerelli, on disease severity and incidence in eight potato cultivars was analyzed. Both haplotypes of Lso induced tuber symptoms. In general, Lso B caused higher incidence of symptoms, and greater reduction in tubers compared with Lso A. Lso B was associated with more severe tuber symptoms, producing fewer mild or moderate tuber symptoms. Lso A was associated with less severe tuber symptoms, despite being able to induce severe symptoms. Disease incidence, tuber yield, and symptom severity ratings were not dependent upon the psyllid haplotype transmitting the pathogen, suggesting that pathogen, not insect haplotype affects Lso transmission.     

Why are plant pathogens under-represented in eco-climatic niche modelling?

Abstract

Eco-climatic niche models are powerful tools for assessing the potential range of plant pests and pathogens, widely applied in comprehensive pest risk assessments globally. We conducted a bibliometric analysis comparing the number of CLIMEX models developed for plant pathogens and plant arthropod pests. We found that plant pathogens were statistically significantly under-represented, with fungal plant pathogens less than half as likely as plant insect pests to be the subject of a published CLIMEX niche model. We explore key factors that may account for this disparity, including inconsistent experimental paradigms and lack of cross-disciplinary (i.e., plant pathology and modelling) expertise.     

Characterizing the APEC pathotype

The purpose of this study was to compare avian pathogenic Escherichia coli (APEC) isolates to fecal isolates of apparently healthy poultry (avian fecal E. coli or AFEC) by their possession of various traits in order to ascertain whether APEC and AFEC are distinct and if the APEC strains constitute a distinct pathotype. Four hundred and fifty-one APEC and one hundred and four AFEC isolates were examined for possession of traits associated with the virulence of human extraintestinal pathogenic E. coli (ExPEC) as well as APEC. Several of the genes occurred in the majority of APEC and only infrequently in AFEC, including cvaC, iroN, iss, iutA, sitA, tsh, fyuA, irp2, and ompT. Of these genes, several have been found on large plasmids in APEC. Other genes occurred in significantly more APEC than AFEC but did not occur in the majority of APEC. Isolates were also evaluated by serogroup, lactose utilization, and hemolytic reaction. Twenty-nine and a half percent of the APEC and forty-two and three tenths percent of the AFEC were not serogrouped because they were not typeable with standard antisera, typed to multiple serogroups, were rough, autoagglutinated, or were not done. Around 65% of the typeable APEC (205 isolates) and AFEC (41 isolates) were classified into shared serogroups, and about a third of both fell into APEC- (113 isolates) or AFEC- (19 isolates) unique serogroups. Most were able to use lactose. No isolate was hemolytic. Overall, the majority of the APEC isolates surveyed shared a common set of putative virulence genes, many of which have been localized to an APEC plasmid known as pTJ100. This common set of genes may prove useful in defining an APEC pathotype.     

How well do Australian women comply with dietary guidelines?

OBJECTIVE: To investigate the proportion of middle-aged Australian women meeting national dietary recommendations and its variation according to selected sociodemographic and behavioural characteristics. DESIGN: This cross-sectional population-based study used a food-frequency questionnaire to investigate dietary patterns and compliance with 13 commonly promoted dietary guidelines among a cohort of middle-aged women participating in the Australian Longitudinal Study on Women's Health. SETTING: Nation-wide community-based survey. SUBJECTS: A total of 10,561 women aged 50-55 years at the time of the survey in 2001. RESULTS: Only about one-third of women complied with more than half of the guidelines, and only two women in the entire sample met all 13 guidelines examined. While guidelines for meat/fish/poultry/eggs/nuts/legumes and 'extra' foods (e.g. ice cream, chocolate, cakes, potatoes, pizza, hamburgers and wine) were met well, large percentages of women (68-88%) did not meet guidelines relating to the consumption of breads, cereal-based foods and dairy products, and intakes of total and saturated fat and iron. Women working in lower socio-economic status occupations, and women living alone or with people other than a partner and/or children, were at significantly increased risk of not meeting guidelines. CONCLUSIONS: The present results indicate that a large proportion of middle-aged Australian women are not meeting dietary guidelines. Without substantial changes in their diets, and help in making these changes, current national guidelines appear unachievable for many women.     

A common fold mediates vertebrate defense and bacterial attack

Proteins containing membrane attack complex/perforin (MACPF) domains play important roles in vertebrate immunity, embryonic development, and neural-cell migration. In vertebrates, the ninth component of complement and perforin form oligomeric pores that lyse bacteria and kill virus-infected cells, respectively. However, the mechanism of MACPF function is unknown. We determined the crystal structure of a bacterial MACPF protein, Plu-MACPF from Photorhabdus luminescens, to 2.0 angstrom resolution. The MACPF domain reveals structural similarity with poreforming cholesterol-dependent cytolysins (CDCs) from Gram-positive bacteria. This suggests that lytic MACPF proteins may use a CDC-like mechanism to form pores and disrupt cell membranes. Sequence similarity between bacterial and vertebrate MACPF domains suggests that the fold of the CDCs, a family of proteins important for bacterial pathogenesis, is probably used by vertebrates for defense against infection.     

Global food security,biodiversity conservation and the future of agricultural intensification

There is vigorous debate about the potential for reforestation to offset losses in biodiversity associated with tropical deforestation, but a scarcity of good data. We quantified developmental trajectories following active restoration (replanting) of deforested pasture land to tropical Australian rainforest, using 20 different bird community indicators within chronosequences of multiple sites. Bird species composition in restored sites (1–24 years old) was intermediate between that of reference sites in pasture and primary rainforest. Total species richness was much less sensitive to land cover change than composition indicators, because of contrasting species-specific response patterns. For example, open-country (grassland/wetland) bird species declined in richness and abundance with increasing site age, while rainforest-dependent species increased. Results from two different landscapes (uplands and lowlands) were remarkably consistent, despite differing bird assemblages. After 10 years, restored sites averaged about half the number of rainforest-dependent bird species typical of rainforest. Mean values at around 20 years overlapped with the “poorest” rainforest reference sites, but projections suggest that >150 years are required to reach mean rainforest levels, and high variability among sites means that many were not on track towards ever achieving a rainforest-like bird community. Regional rainforest endemics were half as likely to occupy older revegetated sites as non-endemic rainforest-dependent species. Between-site variability and slow colonisation by regional endemics strongly constrain the potential of rainforest restoration to offset the biodiversity impacts of tropical deforestation. The results also mean that ongoing monitoring of biodiversity is an essential part of restoration management.