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Microbial Habitat (microbial + habitat)

Distribution by Scientific Domains

Life Sciences	75%

Selected Abstracts

Leaf Associated Microbial Activities in a Stream Affected by Acid Mine Drainage

INTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 5-6 2004
Jeanette SchliefArticle first published online: 23 NOV 200
Abstract Microbial activity was assessed on birch leaves and plastic strips during 140 days of exposure at three sites in an acidic stream of the Lusatian post-mining landscape, Germany. The sites differed in their degrees of ochre deposition and acidification. The aim of the study was (1) to follow the microbial activities during leaf colonization, (2) to compare the effect of different environmental conditions on leaf associated microbial activities, and (3) to test the microbial availability of leaf litter in acidic mining waters. The activity peaked after 49 days and subsequently decreased gradually at all sites. A formation of iron plaques on leaf surfaces influenced associated microbial activity. It seemed that these plaques inhibit the microbial availability of leaf litter and serve as a microbial habitat by itself. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Mutans streptococci in subgingival plaque of treated and untreated patients with periodontitis

JOURNAL OF CLINICAL PERIODONTOLOGY, Issue 7 2001
W. A. Van Der Reijden
Abstract Background: The etiology of root caries is thought to be identical to coronal caries, though root caries seem to be more complicated because of the higher susceptibility of exposed roots (dentin) by periodontal therapy to demineralization than intact enamel. This implies that mutans streptococci are the most likely pathogens in the development of root caries. Although it is known that both the numbers of mutans streptococci and the frequency of isolation in root caries lesions are negatively correlated with the distance from the gingival margin, the subgingival sulcus has not been considered a possible habitat for mutans streptococci. However, subgingival occurence of mutans streptococci in both untreated and treated periodontal patients has not been documented well in the literature. Objective: To investigate the presence and levels of mutans streptococci in the subgingival plaque of patients (n=154) in different stages of periodontal therapy. The subgingival sulcus may be a possible habitat for mutans streptococci. This localisation of mutans streptococci may be of importance in the development of root caries after periodontal surgery. Materials and methods: In this cross-sectional study, subgingival plaque samples from 154 consecutive adult periodontitis patients were tested for presence and levels of mutans streptococci and putative periodontal pathogens by anaerobic cultures. These patients were divided into 4 groups based on their stage of periodontal treatment: (1) untreated patients; (2) patients after initial periodontal therapy only; (3) patients in the maintenance phase who not underwent periodontal surgery; (4) patients after periodontal surgery. Results: The prevalence of mutans streptococci in the 4 study groups varied from 82% in untreated patients to 94% in maintenance patients. The mean proportion of mutans streptococci was 6.65% in maintenance patients versus 1.86% in untreated patients (p=0.005) and 2.51% in patients after scaling and root planing (p=0.041). Conclusions: The subgingival area is a microbial habitat for mutans streptococci that may be of importance in the development of root caries in periodontitis patients. Zusammenfassung Hintergrund: Es wird angenommen, dass die Ätiologie der Wurzelkaries und der Kronenkaries übereinstimmen, obwohl die Entstehung von Wurzelkaries komplizierter zu sein scheint wegen der erhöhten Empfindlichkeit entblößter Wurzeln (Dentin) für Demineralisation im Vergleich zu gesundem Schmelz. Das bedeutet, dass MS die wahrscheinlichsten Pathogene für die Entstehung der Wurzelkaries sind. Obwohl bekannt ist, dass die Zahl der MS und die Häufigkeit ihres Nachweises aus Wurzelkariesläsionen negativ mit dem Abstand vom Gingivarand korrelieren, wurde die subgingivale Region bisher nicht als möglicher Lebensraum für MS erwogen. Das subgingivale Vorkommen von MS bei behandelten und unbehandelten Parodontitispatienten ist in der Literatur nicht gut dokumentiert. Die subgingivale Region könnte ein möglicher Lebensraum für MS und diese Lokalisation bedeutsam für die Entstehung von Wurzelkaries nach parodontaler Therapie sein. Zielsetzung: Untersuchung des Vorkommens und der Menge von MS in der subgingivalen Plaque von Patienten zu unterschiedlichen Zeitpunkten parodontaler Therapie. Material und Methoden: In einer Querschnittsstudie wurden subgingivale Plaqueproben von 154 Patienten mit Erwachsenenparodontitis auf das Vorkommen und den Anteil von MS und putativer Parodontalpathogene in anaerober Kultur untersucht. Die Patienten wurden nach dem Stadium der parodontalen Therapie in 4 Gruppen unterteilt: (1) unbehandelte Patienten (n=51), (2) Patienten nach abgeschlossener Initialtherapie (Mundhygieneunterweisungen sowie Scaling und Wurzelglättung [SRP]) (n=41), (3) Patienten in der unterstützenden Parodontitistherapie (UPT), die nicht parodontalchirurgisch behandelt worden waren (n=48), und (4) Patienten nach Parodontalchirurgie (n=14). Ergebnisse: Die Prävalenz der MS variierte in den 4 Untersuchungsgruppen von 82% bei unbehandelten bis 94% bei UPT-Patienten. Der mittlere Anteil der MS an subgingivaler Plaque lag bei 6.65% (UPT) im Vergleich zu 1.86% (unbehandelte Parodontitis) (p=0.005) bzw. zu 2.51% (SRP) (p=0.041) und 2.18% nach Parodontalchirurgie (n.s.) Schlußfolgerungen: Die subgingivale Region ist ein Lebensraum für MS, die eine Bedeutung für die Pathogenese der Wurzelkaries bei Patienten mit Parodontitis haben könnte. Résumé L'étiologie des caries radiculaires semble étre identique à celle des caries coronaires bien que les caires radiculaires paraîssent plus compliquées vu la susceptibilité plus importante des racines exposées (dentine) par le traitement parodontal à la même déminéralisation que ne l'est l'émail intact. Ceci a comme conséquence que les Streptocoques mutans sont vraisemblabement les pathogènes les plus problables dans le dévelopment des caries radicularies. Bien qu'il soit connu que les nombres de Streptocoques mutans autant que la fréquence de l'isolation des lésions carieuses radiculaires soient en corrélation négative avec la distance depuis la gencive marginale, le sulcus gingival n'a pas été considéré comme habitat possible pour les Streptocoques mutans. Cependant, l'occurence sous-gingivale des Streptocoques mutans chez les patients avec parodontite traitée ou non n'a pas été suffisamment documentée dans la littérature. Le but de cette étude a été d'analyser la présence et les niveaux de Streptocoques mutans dans la plaque sous-gingivale de 154 patients à différentes étapes de leur traitement parodontale. Le sillon sous-gingival pourrait dont être un habitat possible pour les Streptocoques mutans. Cette localisation peut être importante dans le dévelopment des caries radiculaires après le traitement parodontal. Dans cette étude croisée des échantillons de plaque sous-gingivale ont été prélevés chez 154 patients adultes avec parodontite pour vérifier la présence et les niveaux de Streptocoques mutans et d'autres pathogènes parodontaux putatifs par culture anaérobie. Les patients étaient divisés en 4 groupes suivant le stade de leur traitement parodontal: non-traité, traitement initial seulement, phase de maintien mais sans chirurgie, et patient après chirurgie parodontale. La fréquence globale des Streptocoques mutans dans les 4 goupes variaient de 82% chez les patients non-traités à 94% chez ceux au stade de maintenance. La proportion moyenne de Streptocoques mutansétaient de 6.65% chez les patients en maintenance versus 1.86% chez les patients non-traités (p=0.005) et de 2.51% chez les patients après détartrage et surfaçage radiculaire (p=0.041). L'aire sous-gingivale est donc un habitat microbien pour les Streptocoques mutans qui pourraient être assez importants dans le développement des caries radiculaires chez les patients souffrant de parodontite. [source]

Limits of life in MgCl2 -containing environments: chaotropicity defines the window

ENVIRONMENTAL MICROBIOLOGY, Issue 3 2007
John E. Hallsworth
Summary The biosphere of planet Earth is delineated by physico-chemical conditions that are too harsh for, or inconsistent with, life processes and maintenance of the structure and function of biomolecules. To define the window of life on Earth (and perhaps gain insights into the limits that life could tolerate elsewhere), and hence understand some of the most unusual biological activities that operate at such extremes, it is necessary to understand the causes and cellular basis of systems failure beyond these windows. Because water plays such a central role in biomolecules and bioprocesses, its availability, properties and behaviour are among the key life-limiting parameters. Saline waters dominate the Earth, with the oceans holding 96.5% of the planet's water. Saline groundwater, inland seas or saltwater lakes hold another 1%, a quantity that exceeds the world's available freshwater. About one quarter of Earth's land mass is underlain by salt, often more than 100 m thick. Evaporite deposits contain hypersaline waters within and between their salt crystals, and even contain large subterranean salt lakes, and therefore represent significant microbial habitats. Salts have a major impact on the nature and extent of the biosphere, because solutes radically influence water's availability (water activity) and exert other activities that also affect biological systems (e.g. ionic, kosmotropic, chaotropic and those that affect cell turgor), and as a consequence can be major stressors of cellular systems. Despite the stressor effects of salts, hypersaline environments can be heavily populated with salt-tolerant or -dependent microbes, the halophiles. The most common salt in hypersaline environments is NaCl, but many evaporite deposits and brines are also rich in other salts, including MgCl2 (several hundred million tonnes of bischofite, MgCl2·6H2O, occur in one formation alone). Magnesium (Mg) is the third most abundant element dissolved in seawater and is ubiquitous in the Earth's crust, and throughout the Solar System, where it exists in association with a variety of anions. Magnesium chloride is exceptionally soluble in water, so can achieve high concentrations (> 5 M) in brines. However, while NaCl-dominated hypersaline environments are habitats for a rich variety of salt-adapted microbes, there are contradictory indications of life in MgCl2 -rich environments. In this work, we have sought to obtain new insights into how MgCl2 affects cellular systems, to assess whether MgCl2 can determine the window of life, and, if so, to derive a value for this window. We have dissected two relevant cellular stress-related activities of MgCl2 solutions, namely water activity reduction and chaotropicity, and analysed signatures of life at different concentrations of MgCl2 in a natural environment, namely the 0.05,5.05 M MgCl2 gradient of the seawater : hypersaline brine interface of Discovery Basin , a large, stable brine lake almost saturated with MgCl2, located on the Mediterranean Sea floor. We document here the exceptional chaotropicity of MgCl2, and show that this property, rather than water activity reduction, inhibits life by denaturing biological macromolecules. In vitro, a test enzyme was totally inhibited by MgCl2 at concentrations below 1 M; and culture medium with MgCl2 concentrations above 1.26 M inhibited the growth of microbes in samples taken from all parts of the Discovery interface. Although DNA and rRNA from key microbial groups (sulfate reducers and methanogens) were detected along the entire MgCl2 gradient of the seawater : Discovery brine interface, mRNA, a highly labile indicator of active microbes, was recovered only from the upper part of the chemocline at MgCl2 concentrations of less than 2.3 M. We also show that the extreme chaotropicity of MgCl2 at high concentrations not only denatures macromolecules, but also preserves the more stable ones: such indicator molecules, hitherto regarded as evidence of life, may thus be misleading signatures in chaotropic environments. Thus, the chaotropicity of MgCl2 would appear to be a window-of-life-determining parameter, and the results obtained here suggest that the upper MgCl2 concentration for life, in the absence of compensating (e.g. kosmotropic) solutes, is about 2.3 M. [source]

Distribution, phylogenetic diversity and physiological characteristics of epsilon- Proteobacteria in a deep-sea hydrothermal field

ENVIRONMENTAL MICROBIOLOGY, Issue 10 2005
Satoshi Nakagawa
Summary Epsilon- Proteobacteria is increasingly recognized as an ecologically significant group of bacteria, particularly in deep-sea hydrothermal environments. In this study, we studied the spatial distribution, diversity and physiological characteristics of the epsilon- Proteobacteria in various microbial habitats in the vicinity of a deep-sea hydrothermal vent occurring in the Iheya North field in the Mid-Okinawa Trough, by using culture-dependent and -independent approaches. The habitats studied were inside and outside hydrothermal plume, and annelid polychaete tubes. In addition, we deployed colonization devices near the vent emission. The polychaete tubes harboured physiologically and phylogenetically diverse microbial community. The in situ samplers were predominantly colonized by epsilon -Proteobacteria. Energy metabolism of epsilon- Proteobacteria isolates was highly versatile. Tree topology generated from the metabolic traits was significantly different (P = 0.000) from that of 16S rRNA tree, indicating current 16S rRNA gene-based analyses do not provide sufficient information to infer the physiological characteristics of epsilon- Proteobacteria. Nevertheless, culturability of epsilon- Proteobacteria in various microbial habitats differed among the phylogenetic subgroups. Members of Sulfurimonas were characterized by the robust culturability, and the other phylogenetic subgroups appeared to lose culturability in seawater, probably because of the sensitivity to oxygen. These results provide new insight into the ecophysiological characteristics of the deep-sea hydrothermal vent epsilon- Proteobacteria, which has never been assessed by comparative analysis of the 16S rRNA genes. [source]