The bacterial pollution of coastal waters of the southern suburbs of Tunis

The authors present in this paper a study of the bacterian pollution of inshored waters of southern suburbs of Tunis, on the basis of 180 samples collected in 15 different stations, 15 monthly (one for each station). Two districts have been considered: Ez-Zahra and Hammam-Lif. The two districts are submitted to an important bacterian pollution, mainly due to human factor but also to geographical and geomorphological data, to physico-chemical parameters and to some biological characters.     

Bacterial pollution of seawater: comparison of technics of sampling and analysis

From sampling in three areas neighbouring Tunis, the first polluted, the second contaminated and the third clean, the authors point out that the technic of multiple samples using the "Lactose Broth" is the most sensible to faecal pollution.     

Bacterial pollution of the lagoon of Tunis

The authors present in this paper a study about the bacterian pollution of the lagoon of Tunis based on 120 samples collected in 10 different stations. This study points out that the lagoon is polluted (50.8% of the samples) mostly in autumn and in winter. The pollution is exogenous, chiefly caused by the rain spreading over polluted waters of wastes and of rivers, and also by the action of the winds and of the currents on the sediments hosting microbiological parameters of faecal pollution.     

Bacterial pollution in the coastal waters of the suburbs north and south of Tunis

The inshore waters of Northern and Southern suburbs of Tunis are chiefly polluted aroud urban cities. The pollution increases with temperature, men (touristes and bathers), the actions of wind and currentology.     

Epiphytic bacterial communities of the alga <Emphasis Type="Italic">Fucus vesiculosus</Emphasis> in oil-contaminated water areas of the Barents Sea

Taxonomic compositions of epiphytic bacterial communities in water areas differing in levels of oil pollution were revealed. In total, 82 bacterial genera belonging to 16 classes and 11 phyla were detected. All detected representatives of epiphytic bacterial communities belonged to the phyla Actinobacteria, Bacteroidetes, Planctomycetes, Proteobacteria, Verrucomicrobia, Acidobacteria, Cyanobacteria, Firmicutes, and Fusobacteria and candidate division TM7. The ratio of the phyla in the communities varied depending on the levels of oil pollution. New data on taxonomic composition of uncultivated epiphytic bacterial communities of Fucus vesiculosus were obtained.     

A gastropod from the tropical Atlantic becomes an established alien in the Mediterranean

We report the occurrence of an established population of the gastropod Mitrella psilla (Duclos, 1846), native on west African coasts of Mauritania, Senegal and Angola, on the shore of La Goulette, Bay of Tunis. The molluscan species of tropical West African affinity hitherto ascertained in the Mediterranean are not aliens, but have a native range which encompasses at least part of the Alboran Sea since historical times. Mitrella psilla appears therefore as the first instance of a mollusc with a tropical Atlantic origin being added to the Mediterranean fauna. The species was found near an important commercial harbour and is presumed to have been introduced by shipping.     

Cloning, structure and expression of the full-size lon gene in Escherichia coli coding for ATP-dependent La-proteinase

Assembly of the full Escherichia coli K-12 lon gene from the EcoRI--SphI fragment of the bacterial DNA ("modified" gene) cloned and sequenced earlier and the PstI fragment of the same DNA containing 3'-terminal region of the lon gene has been performed. Both "modified" and full genes showed all phenotype properties of lon gene. The complete nucleotide sequence of the gene (2770 bp) coding for the 784 amino acid sequence of protease La was determined. Location of catalytically active serine, histidine and aspartic acid residues was suggested, and ATP-binding site found. The lon gene and protease La structures we found are compared with those described independently and differences observed are discussed.     

Sensitivity of mosquito larvae to insecticides in the region of Tunis in 1984 and 1988

Three pesticides were tested in the laboratory (Chlorpirifos, Temephos and Fenthion) against Culex pipiens larvae. The study was conducted in the Area of Tunis during the years 1984 to 1988. After several years of treatment with there organophosphoric compounds, the resistance rates reached by the treated larval population never exceeded 15, which is much lower than the rates observed in other countries.     

Bacterial pollution of Messina coastal waters: a one year study

A year's monitoring of faecal pollution of marine coastal waters surrounding Messina was carried out in 1996/97. The distribution of faecal coliforms was evaluated in 15 stations located along the Sicilian coastline, sampled monthly in coincidence of the two opposing current phases ("montante" and "scendente" currents) which characterise the Straits of Messina. The data obtained provided a complete picture of hygienic-sanitary conditions of the area and highlighted the presence of heavily polluted sites in correspondence with river outflows. Higher bacterial counts were associated with lower salinity values and higher ammonia concentrations; over an annual study, they occurred during the coldest months, showing the negative impact of continental water inputs on the bacteriological quality of coastal waters.     

Flow cytometric analysis of bacterial respiratory and enzymatic activity in the natural aquatic environment

The respiratory and enzymatic activity of bacteria in polluted and unpolluted river water was investigated by flow cytometry. Double staining with 6CFDA (6-carboxy fluorescein diacetate) and PI (propidium iodide) was used to examine bacterial esterase activity. CTC (5-cyano-2,3-ditolyl tetrazolium chloride) was employed as the indicator of bacterial respiration. The ratios of colony-forming units to total bacterial number were less than 2%, except highly polluted sites. The number of respiring bacteria determined by flow cytometry amounted to 10–15% of the total bacterial number at both unpolluted and polluted sampling stations, while it was 30% at the highly polluted station. Almost 50% of total bacteria demonstrated esterase activity in the unpolluted areas, whereas 70–90% of total bacteria retained this enzymatic activity in the polluted areas. Thus, many of the non-culturable bacteria in the natural aquatic environment have enzymatic activity regardless of the pollution level, and 6CFDA was more superior in the sensitivity for the evaluation of physiological activity of bacteria in the natural environment. The ratio of bacteria with esterase activity increased in direct proportion to the pollution level of river water and suggested that this ratio would be a useful indicator in evaluating the pollution levels in an aquatic environment.     

医院公用电话病原菌污染调查及消毒模式

目的:调查医院公用电话污染情况,比较两种不同消毒液对公用电话的消毒效果。方法:分别对公用电话听筒、话筒及手柄(打接电话时手握部位)在未消毒和A组用复方新洁灵、B组用"84"消毒液消毒后分别涂抹采样做细菌培养。结果:未消毒前电话听筒、话筒及手柄细菌污染率A组为96.7%、B组为93.3%,A组用复方新洁灵、B组用"84"消毒液消毒后做细菌培养均符合卫生学标准要求,经x2检验,P<0.01,差异具有统计学意义。结论:未消毒前电话听筒、话筒及手柄细菌污染率90%以上,而复方新洁灵和"84"消毒液对医院公用电话均可以用来消毒,两种消毒剂的消毒效果无明显差异,临床可根据具体情况选用。     

First Biological Data on the Well Established Lessepsian Migrant <Emphasis Type="Italic">Fistularia commersonii</Emphasis> (Fistulariidae) in the Gulf of Tunis (Central Mediterranean)

The present note reports the first study of the Lessepsian migrant, bluespotted cornetfish Fistularia commersonii Rüppell, 1838 from the Gulf of Tunis based on 32 individuals. The male:female ratio was skewed towards females. The length-weight relationship exhibited an isometric growth. Morphometric and meristic characters, information on feeding habits and gonads were also provided. The eventual establishment of F. commersonii within the Mediterranean is then discussed according the available data on reproduction and growth.     

Assessment of the health status of Donax trunculus from the Gulf of Tunis using integrative biomarker indices

For a few years, the littoral of the Gulf of Tunis has been subjected to agricultural activities, industrial, urban and tourist development and consequently submitted to the impact of many chemical and physical stressors. Sub-individual responses (biochemical biomarkers) in bivalves can be used as an early warning system for ecotoxicological risk assessment. However, the influence of many confounding factors such as ecological (e.g. temperature and salinity) or physiological (e.g. reproductive and nutritive status) parameters on biomarker responses must be taken carefully into account. The aim of the present study was to integrate into indices (Integrated Biomarker Response: IBR and Health Status Index: HSI) individual responses of biochemical biomarkers (acetylcholinesterase, catalase, glutathione-S-transferase, thiobarbituric acid reactive substance levels, lactate dehydrogenase and metallothionein-like proteins) and energy reserves (glycogen, lipid levels and total protein concentrations) at sub-individual level, and condition index at individual level in Donax trunculus originating from 4 sites contrasted by their level of contamination in the Gulf of Tunis. Integrated biomarkers indices have been revealed to be efficient and easy tools for environmental managers. Responses of IBR and HSI were compared and their strengths and weaknesses discussed. Results showed that HSI could be an easy tool for risk management whereas IBR results were more informative with regard to the temporal contribution of each biomarker considered in the battery used in the present work. In bivalves from the reference Sidi Jehmi site, the contribution of energy reserves and the condition index reflecting a good general health status clearly influenced the temporal variations of IBR whereas in bivalves from the multi-contaminated Radès Méliane site, temporal variations of IBR were induced mainly by the responses of pollution biomarkers. Previous investigations concerning other level of biological organization (population) are in accordance with the present data (Tlili et al., 2010, Tlili et al., 2011).     

Quantitative PCR for Genetic Markers of Human Fecal Pollution

Assessment of health risk and fecal bacterial loads associated with human fecal pollution requires reliable host-specific analytical methods and a rapid quantification approach. We report the development of quantitative PCR assays for quantification of two recently described human-specific genetic markers targeting Bacteroidales-like cell surface-associated genes. Each assay exhibited a range of quantification from 10 to 1 × 10⁶ copies of target DNA. For each assay, internal amplification controls were developed to detect the presence or absence of amplification inhibitors. The assays predominantly detected human fecal specimens and exhibited specificity levels greater than 97% when tested against 265 fecal DNA extracts from 22 different animal species. The abundance of each human-specific genetic marker in primary effluent wastewater samples collected from 20 geographically distinct locations was measured and compared to quantities estimated by real-time PCR assays specific for rRNA gene sequences from total Bacteroidales and enterococcal fecal microorganisms. Assay performances combined with the prevalence of DNA targets in sewage samples provide experimental evidence supporting the potential application of these quantitative methods for monitoring fecal pollution in ambient environmental waters.Waterborne diseases that originate from human fecal pollution remain a significant public health issue. As a result, a large number of methods have been developed to detect and quantify human fecal pollution (10, 12, 18, 20). The majority of these methods are based on real-time quantitative PCR (qPCR) assays designed to estimate the concentrations of 16S rRNA gene sequences from various subpopulations within the order Bacteroidales. This bacterial order constitutes a large proportion of the normal gut microbiota of most animals, including humans (3, 15, 27). Bacterial 16S rRNA genes are useful as markers because they have relatively low mutation rates (7) and are typically present in multiple operons, increasing template DNA levels available for detection (2, 11, 17, 29). While several studies have demonstrated the value of Bacteroides 16S rRNA gene-based qPCR assays, currently available assays cannot discriminate between several animal sources closely associated with humans, including cats, dogs, and/or swine (10, 12, 18, 20). Alternative qPCR assays targeting genes directly involved in host-specific interactions may be capable of increased discrimination of fecal pollution sources (22, 23) and are needed to complement existing qPCR-based approaches used to identify sources of human fecal pollution.A recent metagenomic survey of a human fecal bacterial community using genome fragment enrichment has led to the identification of hundreds of candidate human fecal bacterium-specific DNA sequences (23). PCR assays targeting two gene sequences encoding a hypothetical protein potentially involved in remodeling of bacterial surface polysaccharides and lipopolysaccharides (assay 19) and a putative RNA polymerase extracytoplasmic function sigma factor (assay 22) from Bacteroidales-like microorganisms exhibited a high level of specificity (100%) for human fecal material (23). However, it remained to be determined whether these reported chromosomal DNA sequences are abundant and uniform enough within human populations to be detected once diluted in the environment. On the basis of these considerations, the next steps toward the application of these gene sequences for water quality monitoring applications were to design qPCR assays for their detection and then to use these assays to evaluate the overall abundance and distribution of these sequences in human populations relative to those of rRNA gene sequences from different currently recognized fecal indicator bacterial groups.Here, we report the development of two qPCR assays for quantification of the human-specific DNA sequences targeted by previously reported PCR assays 19 and 22 (23). Method performance characteristics, including specificity, range of quantification (ROQ), limit of quantification, amplification efficiency, and analytical precision, were defined for each assay. An internal amplification control (IAC) was designed to monitor for the presence of inhibitors commonly associated with environmental sampling that can confound DNA target copy number estimations. Finally, the abundance of each DNA target in primary effluent wastewater samples representative of 20 geographically distinct human populations was measured by qPCR analysis. In addition, the abundances of these human-specific DNA genes in wastewater were compared to those of rRNA genes of Bacteroidales and enterococci, two general fecal indicator bacterial groups that have been widely used for water quality testing.     

Phospholipid Fatty Acid Composition and Heavy Metal Tolerance of Soil Microbial Communities along Two Heavy Metal-Polluted Gradients in Coniferous Forests

The effects of long-term heavy metal deposition on microbial community structure and the level of bacterial community tolerance were studied along two different gradients in Scandinavian coniferous forest soils. One was near the Harjavalta smelter in Finland, and one was at Ronnskar in Sweden. Phospholipid fatty acid (PLFA) analysis revealed a gradual change in soil microbial communities along both pollution gradients, and most of the individual PLFAs changed similarly to metal pollution at both sites. The relative quantities of the PLFAs br18:0, br17:0, i16:0, and i16:1 increased with increasing heavy metal concentration, while those of 20:4 and 18:2(omega)6, which is a predominant PLFA in many fungi, decreased. The fungal part of the microbial biomass was found to be more sensitive to heavy metals. This resulted in a decreased fungal/bacterial biomass ratio along the pollution gradient towards the smelters. The thymidine incorporation technique was used to study the heavy metal tolerance of the bacteria. The bacterial community at the Harjavalta smelter, exposed mainly to Cu deposition, exhibited an increased tolerance to Cu but not to Cd, Ni, and Zn. At the Ronnskar smelter the deposition consisting of a mixture of metals increased the bacterial community tolerance to all tested metals. Both the PLFA pattern and the bacterial community tolerance were affected at lower soil metal concentrations than were bacterial counts and bacterial activities. At Harjavalta the increased Cu tolerance of the bacteria and the change in the PLFA pattern of the microbial community were found at the same soil Cu concentrations. This indicated that the altered PLFA pattern was at least partly due to an altered, more metal-tolerant bacterial community. At Ronnskar, where the PLFA data varied more, a correlation between bacterial community tolerance and an altered PLFA pattern was found up to 10 to 15 km from the smelter. Farther away changes in the PLFA pattern could not be explained by an increased community tolerance to metals.     

Enhancement of the direct antimicrobial activity of Lysep3 against <Emphasis Type="Italic">Escherichia coli</Emphasis> by inserting cationic peptides into its C terminus

Phage lysins are considered promising antimicrobials against resistant bacterial infections. Some lysins have been reported for the prevention and treatment of Gram-positive bacterial infection. Gram-negative bacterial phage lysins, however, can only destroy the bacterial cell wall from inside because of the obstruction of the bacterial outer membrane that prevents direct hydrolysis of the bacterial wall peptidoglycan from the outside, severely restricting the development of lysins against Gram-negative bacteria. In this study, genetic engineering techniques were used to fuse a 5 cationic amino acid polypeptide (KRKRK), a 10 cationic amino acid polypeptide (KRKRKRKRKR), a 15 cationic amino acid polypeptide (KRKRKRKRKRKRKRK), and a polypeptide including both cationic and hydrophobic amino acids (KRKRKFFVAIIP) to the C-terminus of the Escherichia coli phage lysin Lysep3 to obtain four fusion lysins (5aa, 10aa, 15aa, Mix). The bactericidal effects of those four lysins on E. coli were then compared in vitro. Our results showed that the fusion of hydrophobic and positively charged amino acids, Mix, can kill E. coli effectively; the fusion of positively charged amino acids alone at the C-terminus (5aa, 10aa, 15aa) also showed bactericidal activity against E. coli from the outside, with the bactericidal activity gradually increasing with the positive charge at the C-terminus of the lysin. Collectively, improving the positive charge at the C-terminus of E. coli bacteriophage lysin Lysep3 increases its bactericidal ability from outside E. coli, providing a new practical method for the development of anti-Gram-negative bacterial lysins.     

Saturation of the lactate clearance mechanisms different from the "lactate shuttle" determines the anaerobic threshold: prediction from the bioenergetic model

It is demonstrated, that the bioenergetic model combined with the mathematical constraints determined by the experimental knowledge of the aerobic metabolism and the Lohmann reaction dictates the exact lactate (La)-time relationship during exercise. The theory predicts that La is necessarily produced (above the resting baseline), even during extremely low work loads, where the metabolism was usually considered in the past to be "pure" aerobic. The La rate of production increases linearly as a function of the work load. The anaerobic threshold is strictly determined by the saturation of the La clearance mechanisms of the body different from the "La shuttle" and not by the involvement of a sudden increased La production at the cellular level. These results imply that the half time of the PCr breakdown kinetics at the onset of a constant load exercise can be expressed as a function of the onset speed of the aerobic and of the anaerobic metabolism, even in the case of a very low mechanical power. The PCr half-time does not depend on the workload and represents a physiological invariant. The bioenergetic model was created during a long historical period, when it was believed that the La production was not present at all for very low exercise levels but, actually, the bioenergetic model predicts exactly the opposite result!     

Effect of temperature and relative humidity on the cellular defense response of Ephestia kuehniella larvae fed Bacillus thuringiensis

While maintained under all combinations of three temperatures and two RH, fifth instar larvae of the Mediterranean flour moth, Ephestia kuehniella were fed wheat treated with spores and crystals of Bacillus thuringiensis var. kurstaki. Larvae that had fed on wheat with the bacterial preparation contained higher concentrations of nodules in their haemocoel than did larvae fed on wheat without bacteria. Nodule concentrations in larvae fed untreated wheat were unaffected by temperature or relative humidity. Larvae fed treated wheat had higher nodule concentrations at 32 degrees C than at 15 and 23 degrees C, and higher nodule concentrations at a relative humidity of 85% than at 43%. The percentage of larvae that pupated was lower when larvae were fed the bacterial preparation, and was significantly higher at 23 degrees C than at 15 and 32 degrees C, regardless of whether larvae were fed bacteria or not. Less time was required for larvae to develop to pupation at higher temperatures and at higher humidity. Mean time to pupation was lower for bacteria-fed larvae than for those fed untreated wheat, and this appeared to be a result of truncation of the distribution of times to pupation because only rapidly developing larvae survived to pupation.     

Self-Transmissible Mercury Resistance Plasmids with Gene-Mobilizing Capacity in Soil Bacterial Populations: Influence of Wheat Roots and Mercury Addition

A set of mercury resistance plasmids was obtained from wheat rhizosphere soil amended or not amended with mercuric chloride via exogenous plasmid isolation by using Pseudomonas fluorescens R2f, Pseudomonas putida UWC1, and Enterobacter cloacae BE1 as recipient strains. The isolation frequencies were highest from soil amended with high levels of mercury, and the isolation frequencies from unamended soil were low. With P. putida UWC1 as the recipient, the isolation frequency was significantly enhanced in wheat rhizosphere compared to bulk soil. Twenty transconjugants were analyzed per recipient strain. All of the transconjugants contained plasmids which were between 40 and 50 kb long. Eight selected plasmids were distributed among five groups, as shown by restriction digestion coupled with a similarity matrix analysis. However, all of the plasmids formed a tight group, as judged by hybridization with two whole-plasmid probes and comparisons with other plasmids in dot blot hybridization analyses. The results of replicon typing and broad-host-range incompatibility (Inc) group-specific PCR suggested that the plasmid isolates were not related to any previously described Inc group. Although resistance to copper, resistance to streptomycin, and/or resistance to chloramphenicol was found in several plasmids, catabolic sequences were generally not identified. One plasmid, pEC10, transferred into a variety of bacteria belonging to the β and γ subdivisions of the class Proteobacteria and mobilized as well as retromobilized the IncQ plasmid pSUP104. A PCR method for detection of pEC10-like replicons was used, in conjunction with other methods, to monitor pEC10-homologous sequences in mercury-polluted and unpolluted soils. The presence of mercury enhanced the prevalence of pEC10-like replicons in soil and rhizosphere bacterial populations.The potential use of genetically modified bacteria in agriculture has raised questions pertaining to the spread of introduced recombinant DNA through soil bacterial communities. Gene transfer in soil via conjugation has received much attention, and the focus of most studies has been the transfer and fate of introduced plasmids (6, 22, 27–29, 39). Under favorable conditions, in specific soil microhabitats, or under selection conditions, both self-transmissible and mobilizable plasmids present in introduced hosts can be transferred to introduced recipients, as well as to a variety of indigenous bacteria (15, 20, 27, 28, 33). In particular, rhizospheres of crop plants, such as wheat and sugar beet, provide conditions conducive to conjugal plasmid transfer between bacterial inhabitants (15, 36). When genetically modified bacteria are developed as inoculants for the rhizosphere, insertion of heterologous DNA into non-self-transmissible plasmids or the chromosome might restrict conjugal transfer of this DNA to members of the indigenous bacterial community. However, mobilizing or retromobilizing (33) plasmids present in indigenous soil bacteria could potentially still effect the transfer of the less mobile heterologous DNA via chromosome or plasmid mobilization, which may involve cointegration (9, 19, 31). Such plasmids might thus be responsible for the escape of heterologous DNA from genetically modified bacteria introduced into soil.There is a paucity of knowledge concerning the incidence of plasmids with mobilizing capacity in soils and rhizospheres, as well as concerning the effects of soil factors, such as stresses resulting from pollution or from natural causes (e.g., rhizosphere acidity), on plasmid prevalence and transfer (e.g., reference 38). Whereas it has been suggested that chemical stress often does not enhance plasmid incidence in selected soil bacterial populations (40), pollution in river water or mines (in particular mercury pollution) has been found to exert a selective (enhancing) effect (4, 13).Plasmids of environmental bacteria have classically been obtained by endogenous isolation procedures (20). Endogenous isolation implies that putative plasmid hosts with the phenotype of interest are isolated from soil, after which plasmids are extracted from pure cultures of these strains. On the other hand, pioneering studies performed with river stone epilithon (9) and later extended to soil and sediment (32) have shown that plasmids can be obtained directly from indigenous bacterial communities in new hosts by exogenous isolation. In this approach, plasmids are captured in selectable recipient strains by using mating between these strains and the total bacterial community obtained from an environmental sample. Following incubation, the mating mixture is plated with selection for the recipient and an additional marker gene presumedly located on a plasmid present in the indigenous bacteria (6). The advantage of the exogenous isolation procedure is that no culturing step is required in the mating, which thus allows isolation of plasmids from nonculturable hosts. Furthermore, plasmids are directly selected for their transfer capacity, in addition to the presence of a specific selectable marker.In this study, exogenous plasmid isolation was employed to obtain transferable plasmids from soil bacteria by using mercury resistance as the selectable marker. The objective of this work was to gain insight into the potential present in soil bacterial populations to (retro)mobilize genes out of introduced bacteria into members of the soil bacterial community. Since the incidence of plasmids in soil bacteria is likely influenced by soil ecological factors and selection pressure, the presence of wheat roots and selection by mercury (25) were studied as experimental variables.     

Aerobic and facultatively anaerobic bacteria associated with the gut of Canada geese (Branta canadensis) and whistling swans (Cygnus columbianus columbianus)

Aerobic and facultatively anaerobic bacteria from the intestinal tracts of swans and geese were isolated and characterized as part of a larger study of the microbiological effects of migratory waterfowl on water quality. A total of 356 isolates were identified by using rapid identification methods and classified by using numerical taxonomy. A diverse population of bacteria was recovered from the waterfowl, and representative strains could be classified into 21 phena. The majority of the aerobic, heterotrophic bacteria found in the gut of the waterfowl were species of Enterobacteriaceae. Streptococcus. Lactobacillus, and Bacillus. Unfortunately, the birds that were examined did not harbor significant numbers of any waterfowl-specific bacterial species. Thus, it may not be possible to assess microbiological impact of migratory waterfowl by using and "indicator" species since avian fecal pollution could not be distinguished from animal and human fecal pollution.