Bioleaching in brackish waters--effect of chloride ions on the acidophile population and proteomes of model species.

High concentrations of chloride ions inhibit the growth of acidophilic microorganisms used in biomining, a problem particularly relevant to Western Australian and Chilean biomining operations. Despite this, little is known about the mechanisms acidophiles adopt in order to tolerate high chloride ion concentrations. This study aimed to investigate the impact of increasing concentrations of chloride ions on the population dynamics of a mixed culture during pyrite bioleaching and apply proteomics to elucidate how two species from this mixed culture alter their proteomes under chloride stress. A mixture consisting of well-known biomining microorganisms and an enrichment culture obtained from an acidic saline drain were tested for their ability to bioleach pyrite in the presence of 0, 3.5, 7, and 20 g L(-1) NaCl. Microorganisms from the enrichment culture were found to out-compete the known biomining microorganisms, independent of the chloride ion concentration. The proteomes of the Gram-positive acidophile Acidimicrobium ferrooxidans and the Gram-negative acidophile Acidithiobacillus caldus grown in the presence or absence of chloride ions were investigated. Analysis of differential expression showed that acidophilic microorganisms adopted several changes in their proteomes in the presence of chloride ions, suggesting the following strategies to combat the NaCl stress: adaptation of the cell membrane, the accumulation of amino acids possibly as a form of osmoprotectant, and the expression of a YceI family protein involved in acid and osmotic-related stress.

Behavioral and emotional adjustment of teenagers in mainstream school who were born before 29 weeks' gestation.

OBJECTIVES: To investigate behavioral and emotional problems and positive adjustment of 15-to 16-year-olds who were born at extremely low gestational age (ELGA), from the perspective of parents, teachers, and teenagers. METHODS: Prospective follow-up was conducted of birth cohorts, with classroom control subjects. All infants who were born before 29 weeks in 1983-1984 (mean gestational age: 27 weeks) to mothers who resided in 3 regions of the United Kingdom were studied. A total of 82% (179 of 218) of survivors were traced at age 15 to 16. The 150 in mainstream school were compared with age- and gender-matched classroom control subjects (n = 108). Behavioral and emotional problems, delinquency, peer relations, self-esteem, and hobbies, were assessed by standardized, well-validated instruments, including the Strengths and Difficulties Questionnaire, administered by mail to parents, teenagers, and teachers. RESULTS: Parents were more likely to rate ELGA teenagers than control subjects as in the "abnormal" range for hyperactivity (8% vs 1%; difference: 7%; (95% confidence interval [CI]: 2-12), peer relationship problems (19% vs 5%; difference: 14%; 95% CI: 6-21), and emotional problems (18% vs 7%; difference: 11%; 95% CI: 3-19), but not conduct problems (10% vs 5%; difference: 5%; 95% CI: -1 to 12)). Teachers reported a similar pattern. In contrast, compared with control subjects, ELGA teenagers did not rate themselves as having more problems with peers, hyperactivity, conduct, depression, or low self-esteem. They reported more emotional problems but less delinquency, alcohol, cannabis, and other drug use. CONCLUSIONS: Compared with mainstream classmates, children who are born extremely early continue to have higher levels of parent- and teacher-reported emotional, attentional, and peer problems well into their teens. However, despite these problems, they do not show signs of more serious conduct disorders, delinquency, drug use, or depression.

Diversity and specificity of Rhizobium leguminosarum biovar viciae on wild and cultivated legumes.

The symbiotic partnerships between legumes and their root-nodule bacteria (rhizobia) vary widely in their degree of specificity, but the underlying reasons are not understood. To assess the potential for host-range evolution, we have investigated microheterogeneity among the shared symbionts of a group of related legume species. Host specificity and genetic diversity were characterized for a soil population of Rhizobium leguminosarum biovar viciae (Rlv) sampled using six wild Vicia and Lathyrus species and the crop plants pea (Pisum sativum) and broad bean (Vicia faba). Genetic variation among 625 isolates was assessed by restriction fragment length polymorphism (RFLP) of loci on the chromosome (ribosomal gene spacer) and symbiosis plasmid (nodD region). Broad bean strongly favoured a particular symbiotic genotype that formed a distinct phylogenetic subgroup of Rlv nodulation genotypes but was associated with a range of chromosomal backgrounds. Host range tests of 80 isolates demonstrated that only 34% of isolates were able to nodulate V. faba. By contrast, 89% were able to nodulate all the local wild hosts tested, so high genetic diversity of the rhizobial population cannot be ascribed directly to the diversity of host species at the site. Overall the picture is of a population of symbionts that is diversified by plasmid transfer and shared fairly indiscriminately by local wild legume hosts. The crop species are less promiscuous in their interaction with symbionts than the wild legumes.