Are bryophyte communities different from higher‐plant communities? Abundance relations

The considerable differences in biology between bryophytes and higher plants have led to speculation that their community structure might be different. Ten bryophyte communities were sampled for species biomass composition, and for comparison ten higher-plant communities that were similar in physiognomy and in total community biomass. The rather insecure theory in the bryophyte literature was distilled into eight quantifiable predictions, which were tested. For seven, there was no sign of the predicted differences: i.e. no indication of the predicted low within-community heterogeneity, higher species richness, more variable species richness, lower rank consistency, a poor fit for the geometric model of RAD (relative abundance distribution), better fit for the broken-stick and general-lognormal RAD models with general-lognormal parameter γ deviating further from 1.0, or of a good fit for the Zipf-Mandelbrot RAD model. However, evenness was, on average, significantly (p=0.005) less in the bryophyte communities, using any of four evenness indices. Two possible features of bryophytes are suggested that might cause this: (a) a smaller module (i.e. shoot, leaf) size, allowing species to be present with a lower threshold biomass, and (b) less efficient competitive exclusion among bryophytes because of weaker competition and a predominance of mutualism, as suggested in the literature. However, the striking conclusion from the results is that in spite of all the biological differences between the two groups of organisms, their community organisation is remarkably similar.     

Two glucose transport systems in Bacillus licheniformis.

Bacillus licheniformis NCIB 6346 showed active accumulation of glucose which was inhibited by agents which affect the transmembrane proton gradient. Phosphotransferase (PTS) activity, identified as phosphoenolpyruvate-dependent phosphorylation of glucose, was found in cell extracts but could not be demonstrated in cells permeabilized with toluene when assays were conducted at pH 6.6. The same was true for mannitol and fructose phosphotransferase activities. Cells grown on fructose accumulated glucose at a slower rate than glucose-grown cells, and extracts prepared from them did not contain glucose PTS activity. Examination of the effects of analogs on glucose uptake and phosphorylation showed that 2-deoxyglucose was not a PTS substrate, but did markedly inhibit glucose uptake, with stronger inhibition in cells grown on fructose. Glucose accumulation by whole cells grown on glucose became less sensitive to the uncoupler tetrachlorosalicylanilide (TCS) as the pH was raised from 6.6 to 8.0, while in fructose-grown cells TCS was equally effective across this pH range. PTS activity was exhibited by toluene-treated cells at pH 7.5 and above, although the system itself in extracts was not affected by pH in the range of 5.0 to 8.0. The results are consistent with the presence of two glucose transport systems, one a PTS and the other operating by an alternative mechanisms, and suggest that the PTS in B. licheniformis may be regulated in a pH-dependent manner.     

Isolation and characterization of anti-Salmonella lactic acid bacteria from the porcine gastrointestinal tract

AIMS: To identify lactic acid bacteria (LAB) of porcine intestinal origin with anti-Salmonella activity. METHODS AND RESULTS: Samples were obtained from pig faeces and caeca and screened for the presence of anti-Salmonella LAB. The 11 most promising isolates were identified as belonging to the genera Lactobacillus and Pediococcus. The LAB exhibited large variation in their ability to survive in simulated gastric juice at pH 1.85. While Lactobacillus johnsonii species survived at levels of 80% for up to 30 min, Lactobacillus pentosus species declined to <0.001% in that time. All isolates tolerated porcine bile at a concentration of 0.3% (w/v), with some isolates capable of growth in the presence of up to 5% (w/v) bile. The ability of the LAB isolates to prevent Salmonella invasion of intestinal epithelial HT-29 cells varied, with reductions of between 30% (Lact. pentosus) and 80% (Lactobacillus murinus spp.) observed. CONCLUSIONS: LAB of porcine origin were observed to survive simulated passage through the GIT and inhibit growth of Salmonella and its invasion of the intestinal epithelium. SIGNIFICANCE AND IMPACT OF THE STUDY: The data demonstrate that some porcine intestinal LAB isolates may offer potential as probiotics for the reduction of Salmonella carriage in pigs.     

A method for electrotransformation of Bacillus licheniformis NCIB 6346 by plasmid DNA

Summary An electroporation procedure was developed for transformation of Bacillus licheniformis NCIB 6346 by plasmids. Electrotransformation of a related industrial strain is also reported.     

Bacteria as vectors for gene therapy of cancer

Anti-cancer therapy faces major challenges, particularly in terms of specificity of treatment. The ideal therapy would eradicate tumor cells selectively with minimum side effects on normal tissue. Gene or cell therapies have emerged as realistic prospects for the treatment of cancer, and involve the delivery of genetic information to a tumor to facilitate the production of therapeutic proteins. However, there is still much to be done before an efficient and safe gene medicine is achieved, primarily developing the means of targeting genes to tumors safely and efficiently. An emerging family of vectors involves bacteria of various genera. It has been shown that bacteria are naturally capable of homing to tumors when systemically administered resulting in high levels of replication locally. Furthermore, invasive species can deliver heterologous genes intra-cellularly for tumor cell expression. Here, we review the use of bacteria as vehicles for gene therapy of cancer, detailing the mechanisms of action and successes at preclinical and clinical levels.     

Non-viral in vivo immune gene therapy of cancer: combined strategies for treatment of systemic disease

Many patients with various types of cancers have already by the time of presentation, micrometastases in their tissues and are left after treatment in a minimal residual disease state [Am J Gastroenterol 95(12), 2000]. To prevent tumour recurrence these patients require a systemic based therapy, but current modalities are limited by toxicity or lack of efficacy. We have previously reported that immune reactivity to the primary tumour is an important regulator of micrometastases and determinant of prognosis. This suggests that recruitment of specific anti-tumour mechanisms within the primary tumour could be used advantageously for tumour control as either primary or neo-adjuvant treatments. Recently, we have focused on methods of stimulating immune eradication of solid tumours and minimal residual disease using gene therapy approaches. Gene therapy is now a realistic prospect and a number of delivery approaches have been explored, including the use of viral and non-viral vectors. Non-viral vectors have received significant attention since, in spite of their relative delivery inefficiency, they may be safer and have greater potential for delivery of larger genetic units. By in vivo electroporation of the primary tumour with plasmid expressing GM-CSF and B7-1, we aim to stimulate immune eradication of the treated tumour and associated metastases. In this symposium report, we describe an effective gene based approach for cancer immunotherapy by inducing cytokine and immune co-stimulatory molecule expression by the growing cells of the primary tumour using a plasmid electroporation gene delivery strategy. We discuss the potential for enhancement of this therapy by its application as a neoadjuvant to surgical excision and by its use in combination with suppressor T cell depletion.This article is a symposium paper from the Annual Meeting of the “International Society for Cell and Gene Therapy of Cancer”, held in Shenzhen, China, on 9–11 December 2005.     

Ex Vivo Culture of Patient Tissue & Examination of Gene Delivery

This video describes the use of patient tissue as an ex vivo model for the study of gene delivery. Fresh patient tissue obtained at the time of surgery is sliced and maintained in culture. The ex vivo model system allows for the physical delivery of genes into intact patient tissue and gene expression is analysed by bioluminescence imaging using the IVIS detection system. The bioluminescent detection system demonstrates rapid and accurate quantification of gene expression within individual slices without the need for tissue sacrifice. This slice tissue culture system may be used in a variety of tissue types including normal and malignant tissue and allows us to study the effects of the heterogeneous nature of intact tissue and the high degree of variability between individual patients. This model system could be used in certain situations as an alternative to animal models and as a complementary preclinical mode prior to entering clinical trial.Download video file.^{(23M, mov)}