Carbon steel coupons were immersed for 1–8 weeks at ∼1 m deep in a French harbor of the Atlantic coast. The resulting corrosion product layers were characterized by μ-Raman spectroscopy. They ...consisted of an inner stratum of sulfated green rust covered by an outer stratum of lepidocrocite (predominantly), goethite and magnetite. Mackinawite FeS was detected after one month of immersion, but only locally. The bacterial characterization of these layers was coupled to this analysis. The diversity of the culturable bacteria grown in liquid media directly from biofilms or isolated on agar plates was evaluated by 16S rRNA gene sequencing. The microbial diversity was also estimated, without cultivation and after Temporal Temperature Gradient Electrophoresis (TTGE) separation. A moderate biodiversity was found in all cases and different bacteria associated with the redox cycles of Fe and S were identified. Roseobacter, Erythrobacter and Bacillus were dominant among culturable bacteria whereas Sulfurimonas autotrophica, a sulfur-oxidizing bacterium, was detected among the total bacterial community at all immersion times. After one month of immersion, sulfide-producing bacteria were detected, e.g. Desulfovibrio profundus in liquid mixed cultures and Sulfurospirillum arcachonense in the total bacterial community, in agreement with the local identification of FeS by μ-Raman spectroscopy.
•The corrosion product layers are characterized by a moderate bacterial diversity.•A significant discrepancy between the total and culturable bacteria is shown.•FeS and sulfidogenic bacteria are detected locally as soon as one month of immersion.•Sulfated Green Rust is the Fe(II)-based corrosion product in the absence of SRB.
BACKGROUND: Domestic water storage containers constitute major Aedes aegypti breeding sites. We present for the first time a comparative analysis of the bacterial communities associated with Ae. ...aegypti larvae and water from domestic water containers. METHODS: The 16S rRNA-temporal temperature gradient gel electrophoresis (TTGE) was used to identify and compare bacterial communities in fourth-instar Ae. aegypti larvae and water from larvae positive and negative domestic containers in a rural village in northeastern Thailand. Water samples were cultured for enteric bacteria in addition to TTGE. Sequences obtained from TTGE and bacterial cultures were clustered into operational taxonomic units (OTUs) for analyses. RESULTS: Significantly lower OTU abundance was found in fourth-instar Ae. aegypti larvae compared to mosquito positive water samples. There was no significant difference in OTU abundance between larvae and mosquito negative water samples or between mosquito positive and negative water samples. Larval samples had significantly different OTU diversity compared to mosquito positive and negative water samples, with no significant difference between mosquito positive and negative water samples. The TTGE identified 24 bacterial taxa, belonging to the phyla Proteobacteria, Firmicutes, Actinobacteria, Bacteroidetes and TM7 (candidate phylum). Seven of these taxa were identified in larval samples, 16 in mosquito positive and 13 in mosquito negative water samples. Only two taxa, belonging to the phyla Firmicutes and Actinobacteria, were common to both larvae and water samples. Bacilli was the most abundant bacterial class identified from Ae. aegypti larvae, Gammaproteobacteria from mosquito positive water samples, and Flavobacteria from mosquito negative water samples. Enteric bacteria belonging to the class Gammaproteobacteria were sparsely represented in TTGE, but were isolated from both mosquito positive and negative water samples by selective culture. CONCLUSIONS: Few bacteria from water samples were identified in fourth-instar Ae. aegypti larvae, suggesting that established larval bacteria, most likely acquired at earlier stages of development, control the larval microbiota. Further studies at all larval stages are needed to fully understand the dynamics involved. Isolation of enteric bacteria from water samples supports earlier outcomes of E. coli contamination in Ae. aegypti infested domestic containers, suggesting the need to further explore the role of enteric bacteria in Ae. aegypti infestation.
The establishment and development of the intestinal microbiota is known to be associated with profound short- and long-term effects on the health of full-term infants (FTI), but studies are just ...starting for preterm infants (PTI). The data also mostly come from western countries and little information is available for the Middle East. Here, we determined the composition and dynamics of the intestinal microbiota during the first month of life for PTI (n = 66) and FTI (n = 17) in Lebanon. Fecal samples were collected weekly and analyzed by quantitative PCR (q-PCR) and temporal temperature gradient gel electrophoresis (TTGE). We observed differences in the establishment and composition of the intestinal microbiota between the two groups. q-PCR showed that PTI were more highly colonized by Staphylococcus than FTI in the first three weeks of life; whereas FTI were more highly colonized by Clostridium clusters I and XI. At one month of life, PTI were mainly colonized by facultative anaerobes and a few strict anaerobes, such as Clostridium cluster I and Bifidobacterium. The type of feeding and antibiotic treatments significantly affected intestinal colonization. TTGE revealed low species diversity in both groups and high inter-individual variability in PTI. Our findings show that PTI had altered intestinal colonization with a higher occurrence of potential pathogens (Enterobacter, Clostridium sp) than FTI. This suggests the need for intervention strategies for PTI to modulate their intestinal microbiota and promote their health.
•Differences were observed in the establishment and composition of the intestinal microbiota between preterm and full-term infants.•Preterm infants have an altered intestinal microbiota and a delay in colonization by some anaerobes.•Lebanese preterm and full-term infants were highly colonized by Bifidobacterium, a genus known for its beneficial effects.•Types of feeding and antibiotic treatments had significant effects on intestinal colonization in preterm infants.
Background and aim: The colonic microflora is involved in the pathogenesis of Crohn's disease (CD) but less than 30% of the microflora can be cultured. We investigated potential differences in the ...faecal microflora between patients with colonic CD in remission (n=9), patients with active colonic CD (n=8), and healthy volunteers (n=16) using culture independent techniques. Methods: Quantitative dot blot hybridisation with six radiolabelled 16S ribosomal ribonucleic acid (rRNA) targeting oligonucleotide probes was used to measure the proportions of rRNA corresponding to each phylogenetic group. Temporal temperature gradient gel electrophoresis (TTGE) of 16S rDNA was used to evaluate dominant species diversity. Results: Enterobacteria were significantly increased in active and quiescent CD. Probe additivity was significantly lower in patients (65 (11)% and 69 (6)% in active CD and quiescent CD) than in healthy controls (99 (7)%). TTGE profiles varied markedly between active and quiescent CD but were stable in healthy conditions. Conclusion: The biodiversity of the microflora remains high in patients with CD. Enterobacteria were observed significantly more frequently in CD than in health, and more than 30% of the dominant flora belonged to yet undefined phylogenetic groups.
Modifications in microbial colonization of the human gut are believed to affect intestinal homeostasis and increase the risk of gastrointestinal diseases. The present study examined different methods ...for investigating the dynamic characterization of the intestinal microbiota in preterm infants. Fecal samples were collected weekly from ten preterm infants during their stay in a neonatal intensive care unit. The infants had a mean gestational age of 29 weeks (range: 28–32 weeks) and a mean birth weight of 1233
g (range: 935–1450
g). Bacterial colonization was assessed using conventional culture techniques and molecular biological methods. More specifically, the recently developed denaturing high performance liquid chromatography (dHPLC) technique was compared to established methods such as temporal temperature gradient gel electrophoresis (TTGE) and rRNA gene library sequencing. Our results indicate that the gastrointestinal tract of preterm infants, born at a gestational age of less than 33 weeks, has a low biodiversity of mainly, culturable bacteria. Finally, dHPLC was evaluated in terms of speed, labor and sensitivity for its use as a tool to analyze microbial colonization in preterm infants. We found that this technique provided major improvements over gel-based fingerprinting methods, such as TTGE, that are commonly used for studying microbial ecology. As such, it may become a common analytical tool for this purpose.
Bacterial carbonate precipitation has implications in geological processes and important biotechnological applications. Bacteria capable of precipitating carbonates have been isolated from different ...calcium carbonate deposits (speleothems) in caves, soil, freshwater and seawater around the world. However, the diversity of bacteria from calcareous deposits in Colombia, and their ability to precipitate carbonates, remains unknown. In this study, conventional microbiological methods and molecular tools, such as temporal temperature gradient electrophoresis (TTGE), were used to assess the composition of bacterial communities associated with carbonate deposits and drip-waters from two Colombian mines. A genetic analysis of these bacterial communities revealed a similar level of diversity, based on the number of bands detected using TTGE. The dominant phylogenetic affiliations of the bacteria, determined using 16S rRNA gene sequencing, were grouped into two phyla: Proteobacteria and Firmicutes. Within these phyla, seven genera were capable of precipitating calcium carbonates: Lysinibacillus, Bacillus, Strenotophomonas, Brevibacillus, Methylobacterium, Aeromicrobium and Acinetobacter. FTIR and SEM/EDX were used to analyze calcium carbonate crystals produced by isolated Acinetobacter gyllenbergii. The results showed that rhombohedral and angular calcite crystals with sizes of 90μm were precipitated. This research provides information regarding the presence of complex bacterial communities in secondary carbonate deposits from mines and their ability to precipitate calcium carbonate from calcareous deposits of Colombian mines.
AIMS: Casizolu is a traditional Sardinian (Italy) pasta filata cheese made with cow raw milk belonging to Sardo‐Modicana and/or Bruno‐Sarda breeds added with natural whey starter. This work aims to ...describe the traditional technology of this product and to evaluate the microbial groups/species involved in the first month of ripening. METHODS AND RESULTS: Raw milk, curd after stretching and Casizolu cheese samples from two different farmsteads were subjected to enumeration of microbial groups, isolation and genotypic characterization of isolates and PCR temporal temperature gel electrophoresis (TTGE) analysis. The counts of lactobacilli and lactococci groups in raw milk were about 5–6 log UFC ml⁻¹ of milk. These counts tended to increase in curd and cheeses, reaching values higher than 8 log UFC g⁻¹ of cheese. Culture dependent and independent approaches employed in this work highlighted the fundamental role of Lactococcus lactis subsp. lactis, Streptococcus thermophilus and Lactobacillus paracasei in the manufacture and ripening of Casizolu cheese. Other species frequently isolated were Enterococcus durans, Enterococcus faecium, Enterococcus italicus while Enterococcus lactis, Streptococcus parauberis, Lactobacillus plantarum, Lactobacillus pentosus, Lactobacillus brevis, Lactobacillus fermentum and Lactococcus raffinolactis were isolated occasionally. CONCLUSIONS: Lactococcus lactis subsp. lactis, Strep. thermophilus and Lact. paracasei were the principal bacterial species involved in the Casizolu cheese manufacturing and ripening. For the first time, Ent. italicus and Ent. lactis were isolated in the pasta filata cheese. SIGNIFICANCE AND IMPACT OF THE STUDY: This study shows the first data on microbial groups and species involved in the manufacture of Casizolu cheese and highlights the role of Lact. paracasei and Enterococcus spp. from the earliest stages of ripening cheese; furthermore, provides evidence that raw milk cheese is a source of new strains and therefore a reservoir of microbial biodiversity.
The objective of this work was to characterize the traditional cheese, Bouhezza made with raw goat's milk. There were three cheese making performed; two at the laboratory scale (FH1, FH2) and one in ...a farm (FH3). The evaluation consisted in the determination of physico-chemical characteristics, proteolysis, microbiological and sensory status. The microbiological characterization was performed during cheese ripening with identification of lactic acid bacteria by 16S rDNA sequencing using PCR-TTGE. The sensory analysis and volatile profile were determined by GC-MS. The pH decreased during cheese ripening from 4.69 to 3.99. The moisture in defatted cheese was 79.05% and fat-in-dry matter 34.77%, which allowed its classification according to the Codex alimentarius as ripened soft and mid-fat cheese. The urea-PAGE pattern of caseins showed a fast proteolysis, which started from the first day of ripening. The sensory evaluation showed that Bouhezza cheese was salty, spicy and intense in odour and aroma. A total, of 100 volatile compounds were identified, where the main components were carboxylic acids (14 compounds) followed by their esters (32) and alcohols (13), aldehydes (5), ketones (8), terpenes and miscellaneous compounds. This study showed that Bouhezza cheese was considered as a product of satisfactory microbiological quality and rich in LABs whose contribute to its ripening, where many of identified strains were the same as those found in other dairy products. The main sensory descriptors as flavour and odor, was lactic flavor and lactic acidic odor. The products of proteolysis gives to Bouhezza a riches in volatiles and fragrance characteristics, which reflect the uniqueness of this cheese of terroir. Finally, an identity card of the Bouhezza cheese was achieved following results of this study.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Polycyclic aromatic hydrocarbon (PAH) degradation may be increased in plant rhizosphere, but the role of plants in PAH degradation is not clearly understood. We investigated the effect of ryegrass ...root exudates on phenanthrene (PHE) degradation, PHE degrading bacterial population and functional gene expression in sand microcosms inoculated with bacteria from an industrial PAH polluted soil. Dominant bacteria were identified using 16S rDNA based temporal thermal gradient electrophoresis (TTGE). Functional PAH-ring hydroxylating dioxygenase (PAH-RHD
α) genes (DNA) and transcripts (RNA) were quantified through real-time PCR and RT-PCR. Without root exudates PHE degradation was rapid and complete within 5 days.
Herbaspirillum sp. and
Pseudomonas putida were the dominant strains. Percentage of PAH-RHD
α relative to 16S rRNA, both for genes and transcripts, was the highest after only two days and then decreased. With phenanthrene and root exudates as carbon sources, only 50% of the PHE was degraded in 10 days.
P. putida-related bacteria were also detected with other strains related to
Pseudomonas sp. and
Paenibacillus. PHE degradation was reduced, and the percentage of PAH-RHD
α transcripts was lower with root exudates than with only PHE, but increased over the incubation, while PAH-RHD
α gene copy number was higher.
► Microcosms with PHE spiked sand inoculated with soil bacteria were used. ► The effect of root exudates addition on PHE degradation and genes was investigated. ► Without root exudates PHE degradation was rapid and complete within 5 days. ► Root exudates decreased PHE degradation and the percentage of PAH-RHD
α transcripts. ► Partially different dominant bacteria were detected with and without root exudates.
The very-preterm infant gut microbiota is increasingly explored due to its probable role in the development of life threatening diseases. Results of high-throughput studies validate and renew the ...interest in approaches with lower resolution such as PCR-Temporal Temperature Gel Electrophoresis (TTGE) for the follow-up of dominant microbiota dynamics. We report here an extensive longitudinal study of gut colonization in very preterm infants. We explored by 16S rDNA-based PCR-TTGE a total of 354 stool specimens sampled during routine monitoring from the 1(st) to the 8(th) week of life in 30 very pre-term infants born before 30 weeks of gestational age.
Combining comparison with a diversity ladder and sequencing allowed affiliation of 50 Species-Level Operational Taxonomic Units (SLOTUs) as well as semi-quantitative estimation of Operational Taxonomic Units (OTUs). Coagulase-negative staphylococci, mainly the Staphylococcus epidermidis, was found in all the infants during the study period and was the most represented (75.7% of the SLOTUs) from the first days of life. Enterococci, present in 60% of the infants were early, highly represented and persistent colonizers of the premature gut. Later Enterobacteriaceae and the genus Clostridium appeared and were found in 10 (33%) and 21 infants (70%), respectively. We showed a high representation of Veillonella in more than a quarter of the infants and being able to persistently colonize premature gut. The genera Anaerococcus, Aquabacterium, Bacillus, Bifidobacterium, Corynebacterium, Micrococcus, Oceanobacillus, Propionibacterium, Pseudomonas, Rothia, Sarcina, Sneathia and Streptococcus were observed as transient or persistent colonizers, each genus being found in a minority of infants.
Despite low resolution, PCR-TTGE remains complementary to high-throughput sequencing-based approaches because it allows the follow-up of dominant bacteria in gut microbiota in a large longitudinal cohorts of preterm neonates. We described the development of pre-term gut microbiota that should be now replaced regarding the functional role of major OTUs.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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