The effects of a marine fish-farm on the species richness and abundance of molluscs, decapods and echinoderms associated with a "Posidonia oceanica" meadow in Malta (Central Mediterranean)

The composition of the echinoderm, mollusc and decapod assemblages associated with a Posidonia oceanica meadow located close to a fish-farm varied with distance from the cages Three ecological zones were identified. The intermediate zone II (40-160m from the cages) had a higher species richness and abundance than either zones I (nearest the cages) and III (320m from the cages), probably due to the higher production resulting from a moderate level of nutrient enrichment at intermediate distances from the source of pollution.peer-reviewe

Vaccination approaches for the prevention of urinary tract infection

Urinary tract infections (UTIs) are one of the most common infectious diseases of humans, with approximately 150 million cases estimated to occur globally every year. UTIs usually start as a bladder infection (cystitis), but can develop into acute kidney infection (pyelonephritis) and even infection of the bloodstream (urosepsis). The high frequency of UTIs in community and nosocomial settings places an enormous burden on healthcare systems worldwide. Multiple different pathogens cause UTI, with uropathogenic E. coli (UPEC) the most common etiological agent. UTIs caused by these pathogens are increasingly associated with antibiotic resistance, thus severely reducing treatment options and significantly increasing UTI-associated morbidity and mortality. In this review we present an overview of the recent advances in vaccine research targeted towards the prevention of UPEC-mediated UTI. In the context of multidrug resistance, we conclude that vaccination represents a viable approach for the prevention of chronic and recurrent UTI

Motile macroinvertebrate assemblages associated with submerged Posidonia oceanica litter accumulations

In the Mediterranean, seagrass leaf litter derived from Posidonia oceanica beds constitutes an important source of detritus. Large areas with P. oceanica leaf litter are ubiquitous in the infralittoral, but data on the species assemblages characterising this habitat are lacking. Samples of leaf litter were collected in December 2001 from 8 stations in each of two bays on the northern coast of Malta, using a suction sampler. A total of 4794 motile macroinvertebrates comprising 43 species were recorded. Overall, diversity and evenness values were low, however, abundance values were very high. Detritivorous crustaceans were the most abundant taxon (>97 %), with amphipods having the highest abundance (81.8 %). Our results indicate that P. oceanica leaf litter is a distinct habitat that supports characteristic motile macroinvertebrate assemblages dominated by gammarid amphipods. Mediterranean marine Gammarus spp. are typically found in brackish habitats, and only infrequently occur in fully marine waters. However, no sources of brackish water were present in the vicinity of our study sites, which seems to indicate that the occurrence of Gammarus spp. in P. oceanica leaf litter accumulations may be widespread. We suggest that the P. oceanica leaf litter habitat supports unique macroinvertebrate assemblages composed mostly of motile detritivores and which may constitute an important link in transferring production from P. oceanica leaves to higher trophic levels.peer-reviewe

Epithelial Cell Coculture Models for Studying Infectious Diseases: Benefits and Limitations

Countless in vitro cell culture models based on the use of epithelial cell types of single lineages have been characterized and have provided insight into the mechanisms of infection for various microbial pathogens. Diverse culture models based on disease-relevant mucosal epithelial cell types derived from gastrointestinal, genitourinary, and pulmonary organ systems have delineated many key host-pathogen interactions that underlie viral, parasitic, and bacterial disease pathogenesis. An alternative to single lineage epithelial cell monoculture, which offers more flexibility and can overcome some of the limitations of epithelial cell culture models based on only single cell types, is coculture of epithelial cells with other host cell types. Various coculture models have been described, which incorporate epithelial cell types in culture combination with a wide range of other cell types including neutrophils, eosinophils, monocytes, and lymphocytes. This paper will summarize current models of epithelial cell coculture and will discuss the benefits and limitations of epithelial cell coculture for studying host-pathogen dynamics in infectious diseases

Interplay between tolerance mechanisms to copper and acid stress in Escherichia coli

Copper (Cu) is a key antibacterial component of the host innate immune system and almost all bacterial species possess systems that defend against the toxic effects of excess Cu. The Cu tolerance system in Gram-negative bacteria is composed minimally of a Cu sensor (CueR) and a Cu export pump (CopA). The cueR and copA genes are encoded on the chromosome typically as a divergent but contiguous operon. In Escherichia coli, cueR and copA are separated by two additional genes, ybaS and ybaT, which confer glutamine (Gln)-dependent acid tolerance and contribute to the glutamate (Glu)-dependent acid resistance system in this organism. Here we show that Cu strongly inhibits growth of a ∆copA mutant strain in acidic cultures. We further demonstrate that Cu stress impairs the pathway for Glu biosynthesis via glutamate synthase, leading to decreased intracellular levels of Glu. Addition of exogenous Glu rescues the ∆copA mutant from Cu stress in acidic conditions. Gln is also protective but this relies on the activities of YbaS and YbaT. Notably, expression of both enzymes is up-regulated during Cu stress. These results demonstrate a link between Cu stress, acid stress, and Glu/Gln metabolism, establish a role for YbaS and YbaT in Cu tolerance, and suggest that subtle changes in core metabolic pathways may contribute to overcoming host-imposed copper toxicity

Uropathogenic Escherichia coli virulence and innate immune responses during urinary tract infection

Urinary tract infections (UTI) are among the most common infectious diseases of humans and are the most common nosocomial infections in the developed world. It is estimated that 40-50% of women and 5% of men will develop a UTI in their lifetime, and UTI accounts for more than 1 million hospitalizations and $1.6 billion in medical expenses each year in the USA. Uropathogenic Escherichia coli (UPEC) is the primary cause of UTI. This review presents an overview of recent discoveries related to the primary virulence factors of UPEC and major innate immune responses to infection of the lower urinary tract. New and emerging themes in UPEC research are discussed in the context of the interface between host and pathogen

Functional heterogeneity of the UpaH autotransporter protein from uropathogenic Escherichia coli

Uropathogenic Escherichia coli (UPEC) are responsible for the majority of urinary tract infections(UTI). To cause UTI, UPEC must adhere to epithelial cells of the urinary tract and overcome the shear flow forces of urine. This function is primarily mediated by fimbrial adhesins, which mediate specific attachment to host cell receptors. Another group of adhesins that contribute to UPEC mediated UTI are autotransporter (AT) proteins. AT proteins possess a range of virulence properties such as adherence, aggregation, invasion and biofilm formation. One recently characterized AT protein of UPEC is UpaH, a large AIDA-I type AT protein that contributes to biofilm formation and bladder colonization. In this study, we have characterized a series of naturally occurring variants of UpaH. We demonstrate that extensive sequence variation exists within the passenger-encoding domain of UpaH variants from different UPEC strains. This sequence variation is associated with functional heterogeneity with respect to the ability of UpaH to mediate biofilm formation. In contrast, all of the UpaH variants examined retained a conserved ability to mediate binding to extracellular matrix (ECM) proteins. Bioinformatic analysis of the UpaH passenger domain identified a conserved region (UpaHCR) and hydrophobic region (UpaHHR). Deletion of these domains reduced biofilm formation but not binding to ECM proteins. Despite variation in upaH sequence, the transcription of upaH was repressed by a conserved mechanism involving the global regulator H-NS, and mutation of the hns gene relieved this repression. Overall, our findings shed new light on the regulation and function of the UpaH AT protein