Fish oil replacement in current aquaculture feed : is cholesterol a hidden treasure for fish nutrition?

Teleost fish, as with all vertebrates, are capable of synthesizing cholesterol and as such have no dietary requirement for it. Thus, limited research has addressed the potential effects of dietary cholesterol in fish, even if fish meal and fish oil are increasingly replaced by vegetable alternatives in modern aquafeeds, resulting in progressively reduced dietary cholesterol content. The objective of this study was to determine if dietary cholesterol fortification in a vegetable oil-based diet can manifest any effects on growth and feed utilization performance in the salmonid fish, the rainbow trout. In addition, given a series of studies in mammals have shown that dietary cholesterol can directly affect the fatty acid metabolism, the apparent in vivo fatty acid metabolism of fish fed the experimental diets was assessed. Triplicate groups of juvenile fish were fed one of two identical vegetable oil-based diets, with additional cholesterol fortification (high cholesterol, H-Chol) or without (low cholesterol, L-Chol), for 12 weeks. No effects were observed on growth and feed efficiency, however, in fish fed H-Col no biosynthesis of cholesterol, and a remarkably decreased apparent in vivo fatty acid b-oxidation were recorded, whilst in LChol fed fish, cholesterol was abundantly biosynthesised and an increased apparent in vivo fatty acid b-oxidation was observed. Only minor effects were observed on the activity of stearyl-CoA desaturase, but a significant increase was observed for both the transcription rate in liver and the apparent in vivo activity of the fatty acid D-6 desaturase and elongase, with increasing dietary cholesterol. This study showed that the possible effects of reduced dietary cholesterol in current aquafeeds can be significant and warrant future investigations.

Antibiotic resistance in invasive Streptococcus pneumoniae isolates identified in Scotland between 1999 and 2007

Data from 4727 invasive isolates of Streptococcus pneumoniae submitted to the Scottish Haemophilus, Legionella, Meningococcus and Pneumococcus Reference Laboratory between 1999 and 2007 were analysed to establish susceptibility profiles to penicillin, erythromycin and cefotaxime. Pneumococcal resistance to penicillin over the study period remained low, with only 0.2 % (n=7/4727) of isolates falling into this category (MIC ≥2 mg l−1). These isolates have been sporadic, and have mainly represented serogroup 14 (ST9) and 9 (ST156). In comparison, the ‘intermediate sensitivity’ group (MIC 0.12–1 mg l−1) ranged between 2 and 6 % per year, the majority from serogroup 9 (ST156). Over the study period, we found that 12 % (n=585/4727) of isolates were erythromycin-resistant (MIC >0.5 mg l−1), with the majority (n=467; 80 %) of these isolates identified as serogroup 14 (ST9). Cephalosporin resistance (cefotaxime MIC >1 mg l−1) was found in only 0.06 % (n=2/3135) of isolates. Internationally recognized clones (Pneumococcal Molecular Epidemiology Network) accounted for 35 % (n=28/81) of the penicillin non-susceptible isolates and 75 % (n=248/330) of the macrolide-resistant isolates, with ST9 and ST306 predominating. Between 1999 and 2007 we found that 11.6 % (n=18/155) of the penicillin non-susceptible isolates and 4.8 % (n=28/585) of the macrolide-resistant isolates were from serogroups not covered by the 7-valent conjugate pneumococcal vaccine in use in the UK since 2006. Susceptibility to first-line antimicrobial agents for invasive pneumococcal disease in Scotland remained high over the period 1999–2007.

Death or survival from invasive pneumococcal disease in Scotland: associations with serogroups and multilocus sequence types

We describe associations between death from invasive pneumococcal disease (IPD) and particular serogroups and sequence types (STs) determined by multilocus sequence typing (MLST) using data from Scotland. All IPD episodes where blood or cerebrospinal fluid (CSF) culture isolates were referred to the Scottish Haemophilus, Legionella, Meningococcal and Pneumococcal Reference Laboratory (SHLMPRL) from January 1992 to February 2007 were matched to death certification records by the General Register Office for Scotland. This represented 5959 patients. The median number of IPD cases in Scotland each year was 292. Deaths, from any cause, within 30 days of pneumococcal culture from blood or CSF were considered to have IPD as a contributing factor. Eight hundred and thirty-three patients died within 30 days of culture of Streptococcus pneumoniae from blood or CSF [13.95 %; 95 % confidence interval (13.10, 14.80)]. The highest death rates were in patients over the age of 75. Serotyping data exist for all years but MLST data were only available from 2001 onward. The risk ratio of dying from infection due to particular serogroups or STs compared to dying from IPD due to all other serogroups or STs was calculated. Fisher’s exact test with Bonferroni adjustment for multiple testing was used. Age adjustment was accomplished using the Cochran–Mantel–Haenszel test and 95 % confidence intervals were reported. Serogroups 3, 11 and 16 have increased probability of causing fatal IPD in Scotland while serogroup 1 IPD has a reduced probability of causing death. None of the 20 most common STs were significantly associated with death within 30 days of pneumococcal culture, after age adjustment. We conclude that there is a stronger association between a fatal outcome and pneumococcal capsular serogroup than there is between a fatal outcome and ST.

Salicylic acid and its role in defence against plasmodiophora brassicae

Salicylic acid is a crucial plant hormone involved defence responses against biotrophic pathogens. This thesis aimed to induce a defence response against the soil-borne biotroph, Plasmodiophora brassicae, by application of salicylic acid. Using broccoli and Arabidopsis thaliana pathway mutants I have shown that salicylic acid is essential in this interaction.

Transcriptomic characterisation of pigeon ‘milk’ production and its effect on young

Pigeon milk is fed to young pigeons by both their parents. This thesis described the genetic basis of pigeon milk production in the crop and also its effect on young chickens. This revealed that pigeon milk has functional similarities to mammalian milk, and bioactives with future potential in poultry production were identified.

The resurrection plant Sporobolus stapfianus: An unlikely model for engineering enhanced plant biomass?

The resurrection grass Sporobolus stapfianus Gandoger can rapidly recover from extended periods of time in the desiccated state (water potential equilibrated to 2% relative humidity) (Gaff and Ellis, Bothalia 11:305–308 1974; Gaff and Loveys, Transactions of the Malaysian Society of Plant Physiology 3:286–287 1993). Physiological studies have been conducted in S. stapfianus to investigate the responses utilised by these desiccation-tolerant plants to cope with severe water-deficit. In a number of instances, more recent gene expression analyses in S. stapfianus have shed light on the molecular and cellular mechanisms mediating these responses. S. stapfianus is a versatile research tool for investigating desiccation-tolerance in vegetative grass tissue, with several useful characteristics for differentiating desiccation-tolerance adaptive genes from the many dehydration-responsive genes present in plants. A number of genes orthologous to those isolated from dehydrating S. stapfianus have been successfully used to enhance drought and salt tolerance in model plants as well as important crop species. In addition to the ability to desiccate and rehydrate successfully, the survival of resurrection plants in regions experiencing short sporadic rainfall events may depend substantially on the ability to tightly down-regulate cell division and cell wall loosening activities with decreasing water availability and then grow rapidly after rainfall while water is plentiful. Hence, an analysis of gene transcripts present in the desiccated tissue of resurrection plants may reveal important growth-related genes. Recent findings support the proposition that, as well as being a versatile model for devising strategies for protecting plants from water-loss, resurrection plants may be a very useful tool for pinpointing genes to target for enhancing growth rate and biomass production.

Increased Biomass, Seed Yield and Stress Tolerance Is Conferred in Arabidopsis by a Novel Enzyme from the Resurrection Grass Sporobolus stapfianus That Glycosylates the Strigolactone Analogue GR24

Isolation of gene transcripts from desiccated leaf tissues of the resurrection grass, Sporobolus stapfianus, resulted in the identification of a gene, SDG8i, encoding a Group 1 glycosyltransferase (UGT). Here, we examine the effects of introducing this gene, under control of the CaMV35S promoter, into the model plant Arabidopsis thaliana. Results show that Arabidopsis plants constitutively over-expressing SDG8i exhibit enhanced growth, reduced senescence, cold tolerance and a substantial improvement in protoplasmic drought tolerance. We hypothesise that expression of SDG8i in Arabidopsis negatively affects the bioactivity of metabolite/s that mediate/s environmentally-induced repression of cell division and expansion, both during normal development and in response to stress. The phenotype of transgenic plants over-expressing SDG8i suggests modulation in activities of both growth- and stress-related hormones. Plants overexpressing the UGT show evidence of elevated auxin levels, with the enzyme acting downstream of ABA to reduce drought-induced senescence. Analysis of the in vitro activity of the UGT recombinant protein product demonstrates that SDG8i can glycosylate the synthetic strigolactone analogue GR24, evoking a link with strigolactone-related processes in vivo. The large improvements observed in survival of transgenic Arabidopsis plants under cold-, salt- and drought-stress, as well as the substantial increases in growth rate and seed yield under non-stress conditions, indicates that overexpression of SDG8i in crop plants may provide a novel means of increasing plant productivity.

Sporobolus stapfianus, a model desiccation-tolerant grass

Sporobolus stapfianus Gandoger, one of ~40 known ‘anabiotic’grass species (i.e. ‘able to regain vital activity from a state of latent life’), is the most versatile tool for research into desiccation tolerance in vegetative grass tissue. Current knowledge on this species is presented, including the features that suit it for investigations into the plant’s ability to survive dehydration of its leaf protoplasm. The main contributors to desiccation tolerance in S. stapfianus leaves appear to be: accumulation during dehydration of protectants of membranes and proteins; mechanisms limiting oxidative damage; a retention of protein synthetic activity in late stages of drying that is linked with changes in gene expression and in the proteomic array; and an ability to retain net synthesis of ATP during drying. S. stapfianus exemplifies an advanced stage of an evolutionary trend in desiccation tolerant plants towards increased importance of the dehydration phase (for induction of tolerance, for synthesis of protectants and for proteomic changes).