Biofilm formation by Helicobacter pylori

Helicobacter pylori NCTC 11637 produces a water-insoluble biofilm when grown under defined conditions with a high carbon:nitrogen ratio in continuous culture and in 10% strength Brucella broth supplemented with 3 g l-1 glucose. Biofilm accumulated at the air/liquid interface of the culture. Light microscopy of frozen sections of the biofilm material showed few bacterial cells in the mass of the biofilm. The material stained with periodic acid Schiff's reagent. Fucose, glucose, galactose, and glycero-manno-heptose, N-acetylglucosamine and N-acetylmuramic acid were identified in partially purified and in crude material, using gas chromatography and mass spectrometry. The sugar composition strongly indicates the presence of a polysaccharide as a component of the biofilm material. Antibodies (IgG) to partially purified material were found in both sero-positive and sero-negative individuals. Treatment of the biofilm material with periodic acid reduced or abolished immunoreactivity. Treatment with 5 mol l-1 urea at 100 degrees C and with phenol did not remove antigenic recognition by patient sera. The production of a water-insoluble biofilm by H. pylori may be important in enhancing resistance to host defence factors and antibiotics, and in microenvironmental pH homeostasis facilitating the growth and survival of H. pylori in vivo.     

Biofilm formation by Pneumocystis spp

Pneumocystis spp. can cause a lethal pneumonia in hosts with debilitated immune systems. The manner in which these fungal infections spread throughout the lung, the life cycles of the organisms, and their strategies used for survival within the mammalian host are largely unknown, due in part to the lack of a continuous cultivation method. Biofilm formation is one strategy used by microbes for protection against environmental assaults, for communication and differentiation, and as foci for dissemination. We posited that the attachment and growth of Pneumocystis within the lung alveoli is akin to biofilm formation. An in vitro system comprised of insert wells suspended in multiwell plates containing supplemented RPMI 1640 medium supported biofilm formation by P. carinii (from rat) and P. murina (from mouse). Dramatic morphological changes accompanied the transition to a biofilm. Cyst and trophic forms became highly refractile and produced branching formations that anastomosed into large macroscopic clusters that spread across the insert. Confocal microscopy revealed stacking of viable organisms enmeshed in concanavalin A-staining extracellular matrix. Biofilms matured over a 3-week time period and could be passaged. These passaged organisms were able to cause infection in immunosuppressed rodents. Biofilm formation was inhibited by farnesol, a quorum-sensing molecule in Candida spp., suggesting that a similar communication system may be operational in the Pneumocystis biofilms. Intense staining with a monoclonal antibody to the major surface glycoproteins and an increase in (1,3)-beta-D-glucan content suggest that these components contributed to the refractile properties. Identification of this biofilm process provides a tractable in vitro system that should fundamentally advance the study of Pneumocystis.     

Various mechanisms of flagella helicity formation in haloarchaea

The genome of a halophilic archaeon Haloarcula marismortui carries two flagellin genes, flaA2 and flaB. Previously, we demonstrated that the helical flagellar filaments of H. marismortui were composed primarily of flagellin FlaB molecules, while the other flagellin (FlaA2) was present in minor amounts. Mutant H. marismortui strains with either flagellin gene inactivated were obtained. It was shown that inactivation of the flaA2 gene did not lead to changes in cell motility and helicity of the filaments, while the cells with inactivated flaB lost their motility and flagella synthesis was stopped. Two FlaB flagellin forms having different sensitivities to proteolysis were found in the flagellar filament structure. It is speculated that these flagellin forms may ensure the helical filament formation. Moreover, the flagella of a psychrotrophic haloarchaeon Halorubrum lacusprofundi were isolated and characterized for the first time. H. lacusprofundi filaments were helical and exhibited morphological polymorphism, although the genome contained a single flagellin gene. These results suggest that the mechanisms of flagellar helicity may differ in different halophilic archaea, and sometimes the presence of two flagellin genes, in contrast to Halobacterium salinarum, is not necessary for the formation of a functional helical flagellum.     

Biofilm formation by hyperpiliated mutants of Pseudomonas aeruginosa

Under static growth conditions, hyperpiliated, nontwitching pilT and pilU mutants of Pseudomonas aeruginosa formed dense biofilms, showing that adhesion, not twitching motility, is necessary for biofilm initiation. Under flow conditions, the pilT mutant formed mushroom-like structures larger than those of the wild type but the pilU mutant was defective in biofilm formation. Therefore, twitching motility affects the development of biofilm structure, possibly through modulation of detachment.     

Biofilm formation by Legionella spp. in experiment

Ability of biofilm formation was studied in 28 strains belonging to 12 species of Legionella. Optimal conditions for formation of biofilms were ascertained using reference strain Legionella pneumophila Philadelphia 1. Comparative assessment of the ability of Legionella spp. to form biofilms was performed by cultivation in proteosopepton broth (for 96 hours) and in water (for up to 2 weeks). Highest rates of biofilm formation were observed for strains of L. pneumophila and L. longbeachae. Between L. pneumophila strains the most prominent ability to form biofilms was observed in newly isolated strains BLR-05 and TOTAL 1. Opportunity to use different ability of Legionella species to biofilm formation as a epidemiologically significant marker and for modeling of biofilms of Legionella in association with other microorganisms was discussed.     

Biofilm formation by Pseudoalteromonas ruthenica and its removal by chlorine

The distribution of a recently described marine bacterium, SBT 033 GenBank Accession No. AY723742), Pseudoalteromonas ruthenica, at the seawater intake point, outfall and mixing point of an atomic power plant is described, and its ability to form biofilm was investigated. The effectiveness of the antifouling biocide chlorine in the inactivation of planktonic as well as biofilm cells of P. ruthenica was studied in the laboratory. The results show that the planktonic cells were more readily inactivated than the cells enclosed in a biofilm matrix. Viable counting showed that P. ruthenica cells in biofilms were up to 10 times more resistant to chlorine than those in liquid suspension. Using confocal laser scanning microscopy it was shown that significant detachment of P. ruthenica biofilm developed on a glass substratum could be accomplished by treatment with a dose of 1 mg l-1 chlorine. Chlorine-induced detachment led to a significant reduction in biofilm thickness (up to 69%) and substratum coverage (up to 61%), after 5-min contact time. The results show that P. ruthenica has a remarkable ability to form biofilms but chlorine, a common biocide, can be used to effectively kill and detach these biofilms.     

Biofilm formation by bacterial contaminants of fuel ethanol production

Commercial fuel ethanol production facilities were previously shown to have characteristic populations of bacterial contaminants which reduce product yield and are difficult to eradicate. Bacterial contaminants were found, for the first time, to form biofilms under laboratory conditions. Fermentor samples from a commercial fuel ethanol production facility were used to inoculate a biofilm reactor and purified bacterial isolates were identified. Biofilms were composed of many of the same species present in production samples, with lactic acid bacteria predominating. Mention of trade names or commercial products in this article is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture.     

Biofilm formation by a fimbriae-deficient mutant of Actinobacillus actinomycetemcomitans

Actinobacillus actinomycetemcomitans strain 310-TR produces fimbriae and forms a tight biofilm in broth cultures, without turbid growth. The fimbriae-deficient mutant 310-DF, constructed in this study, was grown as a relatively fragile biofilm at the bottom of a culture vessel. Scanning electron microscopy revealed that on glass coverslips, 310-TR formed tight and spherical microcolonies, while 310-DF produced looser ones. These findings suggest that fimbriae are not essential for the surface-adherent growth but are required for enhancing cell-to-surface and cell-to-cell interactions to stabilize the biofilm. Treatment of the 310-DF biofilm with either sodium metaperiodate or DNase resulted in significant desorption of cells from glass surfaces, indicating that both carbohydrate residues and DNA molecules present on the cell surface are also involved in the biofilm formation.     

Biofilm formation in plant-microbe associations

Bacteria adhere to environmental surfaces in multicellular assemblies described as biofilms. Plant-associated bacteria interact with host tissue surfaces during pathogenesis and symbiosis, and in commensal relationships. Observations of bacteria associated with plants increasingly reveal biofilm-type structures that vary from small clusters of cells to extensive biofilms. The surface properties of the plant tissue, nutrient and water availability, and the proclivities of the colonizing bacteria strongly influence the resulting biofilm structure. Recent studies highlight the importance of these structures in initiating and maintaining contact with the host by examining the extent to which biofilm formation is an intrinsic component of plant-microbe interactions.     

Biofilm formation in Streptococcus pneumoniae

Biofilm‐grown bacteria are refractory to antimicrobial agents and show an increased capacity to evade the host immune system. In recent years, studies have begun on biofilm formation by Streptococcus pneumoniae, an important human pathogen, using a variety of in vitro model systems. The bacterial cells in these biofilms are held together by an extracellular matrix composed of DNA, proteins and, possibly, polysaccharide(s). Although neither the precise nature of these proteins nor the composition of the putative polysaccharide(s) is clear, it is known that choline‐binding proteins are required for successful biofilm formation. Further, many genes appear to be involved, although the role of each appears to vary when biofilms are produced in batch or continuous culture. Prophylactic and therapeutic measures need to be developed to fight S. pneumoniae biofilm formation. However, much care needs to be taken when choosing strains for such studies because different S. pneumoniae isolates can show remarkable genomic differences. Multispecies and in vivo biofilm models must also be developed to provide a more complete understanding of biofilm formation and maintenance.     

Nanohaloarchaea as beneficiaries of xylan degradation by haloarchaea

Climate change, desertification, salinisation of soils and the changing hydrology of the Earth are creating or modifying microbial habitats at all scales including the oceans, saline groundwaters and brine lakes. In environments that are saline or hypersaline, the biodegradation of recalcitrant plant and animal polysaccharides can be inhibited by salt-induced microbial stress and/or by limitation of the metabolic capabilities of halophilic microbes. We recently demonstrated that the chitinolytic haloarchaeon Halomicrobium can serve as the host for an ectosymbiont, nanohaloarchaeon ‘Candidatus Nanohalobium constans’. Here, we consider whether nanohaloarchaea can benefit from the haloarchaea-mediated degradation of xylan, a major hemicellulose component of wood. Using samples of natural evaporitic brines and anthropogenic solar salterns, we describe genome-inferred trophic relations in two extremely halophilic xylan-degrading three-member consortia. We succeeded in genome assembly and closure for all members of both xylan-degrading cultures and elucidated the respective food chains within these consortia. We provide evidence that ectosymbiontic nanohaloarchaea is an active ecophysiological component of extremely halophilic xylan-degrading communities (although by proxy) in hypersaline environments. In each consortium, nanohaloarchaea occur as ectosymbionts of Haloferax, which in turn act as scavenger of oligosaccharides produced by xylan-hydrolysing Halorhabdus. We further obtained and characterised the nanohaloarchaea–host associations using microscopy, multi-omics and cultivation approaches. The current study also doubled culturable nanohaloarchaeal symbionts and demonstrated that these enigmatic nano-sized archaea can be readily isolated in binary co-cultures using an appropriate enrichment strategy. We discuss the implications of xylan degradation by halophiles in biotechnology and for the United Nation's Sustainable Development Goals.     

黄色粘球菌基于复杂社会性细胞行为的生物被膜

黄色粘球菌具有多样化的细胞行为,具备典型多细胞水平的社会性特征。其形成的生物被膜是目前认知的最为复杂的单种群细菌生物被膜之一。黄色粘球菌的社会性细胞行为主导了其生物被膜形成过程中的关键环节,包括固体介质表面的细胞运动、群体细胞的捕食、亲缘细胞的识别、子实体的发育、粘孢子的分化以及细胞程序性死亡等行为过程。文中将介绍相关领域的研究进展。     

Biofilm formation by Salmonella enterica serovar Typhimurium colonizing solid tumours

Systemic administration of Salmonella enterica serovar Typhimurium to tumour bearing mice results in preferential colonization of the tumours and retardation of tumour growth. Although the bacteria are able to invade the tumour cells in vitro, in tumours they were never detected intracellularly. Ultrastructural analysis of Salmonella-colonized tumours revealed that the bacteria had formed biofilms. Interestingly, depletion of neutrophilic granulocytes drastically reduced biofilm formation. Obviously, bacteria form biofilms in response to the immune reactions of the host. Importantly, we tested Salmonella mutants that were no longer able to form biofilms by deleting central regulators of biofilm formation. Such bacteria could be observed intracellularly in immune cells of the host or in tumour cells. Thus, tumour colonizing S. typhimurium might form biofilms as protection against phagocytosis. Since other bacteria are behaving similarly, solid murine tumours might represent a unique model to study biofilm formation in vivo.     

Nitrogen metabolism in haloarchaea

The nitrogen cycle (N-cycle), principally supported by prokaryotes, involves different redox reactions mainly focused on assimilatory purposes or respiratory processes for energy conservation. As the N-cycle has important environmental implications, this biogeochemical cycle has become a major research topic during the last few years. However, although N-cycle metabolic pathways have been studied extensively in Bacteria or Eukarya, relatively little is known in the Archaea. Halophilic Archaea are the predominant microorganisms in hot and hypersaline environments such as salted lakes, hot springs or salted ponds. Consequently, the denitrifying haloarchaea that sustain the nitrogen cycle under these conditions have emerged as an important target for research aimed at understanding microbial life in these extreme environments. The haloarchaeon Haloferax mediterranei was isolated 20 years ago from Santa Pola salted ponds (Alicante, Spain). It was described as a denitrifier and it is also able to grow using NO₃ ^-, NO₂ ^- or NH₄ ⁺ as inorganic nitrogen sources. This review summarizes the advances that have been made in understanding the N-cycle in halophilic archaea using Hfx mediterranei as a haloarchaeal model. The results obtained show that this microorganism could be very attractive for bioremediation applications in those areas where high salt, nitrate and nitrite concentrations are found in ground waters and soils.     

Biofilm formation in water cooling systems

Biofilm formation on stainless steel samples immersed in cooling water has been evaluated by exposing metal samples to cooling seawater for 30 days. Anaerobic bacteria were then at 1.6 × 10⁶/cm², with sulphate-reducing species predominating. Aerobic bacteria and fungi were 2600 and 140/cm², respectively. After 60 days, numbers of aerobic microorganisms remained constant whereas the count of anaerobic microorganisms had increased to 1.8×10⁹/cm². Scanning electron microscopy showed the presence of morphologically different microorganisms in deposits and as a mucilaginous net. No signs of corrosion were detected on the stainless steel surface.The authors are with the Departamento de Engenharia Bioquimica Centro de Tecnologia, Bloco E. Universidade Federal do Rio de Janeiro Ilha do Fundão, 21941-900 Rio de Janeiro, Brazil     

Biofilm formation in attached microalgal reactors

The objective of this study was to investigate the fundamental question of biofilm formation. First, a drum biofilm reactor was introduced. The drums were coated with three porous substrates (cotton rope, canvas, and spandex), respectively. The relationships among the substrate, extracellular polymeric substances (EPS), and adhesion ratio were analyzed. Second, a plate biofilm reactor (PBR) was applied by replacing the drum with multiple parallel vertical plates to increase the surface area. The plates were coated with porous substrates on each side, and the nutrients were delivered to the cells by diffusion. The influence of nitrogen source and concentration on compositions of EPS and biofilm formation was analyzed using PBR under sunlight. The results indicated that both substrate and nitrogen were critical on the EPS compositions and biofilm formation. Under the optimal condition (glycine with concentration of 1 g l^?1 and substrate of canvas), the maximum biofilm productivity of 54.46 g m^?2 d^?1 with adhesion ratio of 84.4 % was achieved.     

Biofilm formation by different strains of Salmonella typhimurium in artificial systems

The ability of 14 different strains of Salmonella typhimurium to biofilm formation depending on genotype and culture conditions was investigated in artificial systems: in 96-well plastic microtitre plates, plastic and glass tubes, plastic Petri dishes and on microscope glasses. Quantitative biofilm growth was monitored by using an assay based on crystal violet staining, while planctonic growth in the same cultures was monitored by absorbance in iEMS Reader MF, and qualitatively--by digital photo and visually. Optimal rate between growth and biofilm indications for all strains was determined at initial cell concentration 10(6-7) KOE/ml and culture incubation at t degrees 28 degrees C. The nutrient content of the medium significantly influenced the quantity of produced biofilm. The nutrient broth LB without NaCl was more effective in promoting biofilm formation, than LB itself. The least quantity of biofilm was formed in water. The genotype of the strains also critically influenced the quantity of produced biofilm. Nonmotile mutants cells had reduced ability to form biofilm. RpoS mutant cells produced significantly less biofilm as compared with cells of isogenic parent strains. The chemical content of plastic and glass also influenced biofilm formation.     

Biofilm formation by five species of Candida on three clinical materials

Most recalcitrant infections are associated with colonization and microbial biofilm development. These biofilms are difficult to eliminate by the immune response mechanisms and the current antimicrobial. Fungi can form biofilms on biomaterials commonly used in clinical practice (intravascular catheters, dentures, heart valves, implanted devices, contact lenses and other devices) and are associated with infections.A variety of in vitro models using different substrates/devices have been described. These models have been used to investigate the effect of different variables, including flow, growth time, nutrients and physiological conditions on fungal biofilm formation, morphology and architecture.The purpose of our study is to analyze biofilm formation capacity by 84 strains of Candida spp. (23 C. albicans, 23 C. parapsilosis, 16 C. tropicalis, 17 C. glabrata and 5 C. krusei) on three materials used in medical devices and its quantification using a method based on viable cell count.Under the conditions of our study, all assayed Candida strains have been able to form biofilms. All species showed greater biofilm formation capacity on Teflon™, with the exception of C. glabrata which displayed higher biofilm formation capacity on PVC. Biofilm formation by Candida spp. varies depending on the type of material on which it grows and on the species and strain of Candida.The method we propose could be of great use to deepen scientific knowledge on this subject of remarkable clinical significance, considering the absence of standard biofilm formation and quantification techniques on the catheters and the level of difficulty associated to those available.