Adhesion of Klebsiella oxytoca to bladder or lung epithelial cells is promoted by the presence of other opportunistic pathogens

The intestinal and respiratory tracts of healthy individuals serve as habitats for a diverse array of microorganisms, among which Klebsiella oxytoca holds significance as a causative agent in numerous community- and hospital-acquired infections, often manifesting in polymicrobial contexts. In specific circumstances, K. oxytoca, alongside other constituents of the gut microbiota, undergoes translocation to distinct physiological niches. In these new environments, it engages in close interactions with other microbial community members. As this interaction may progress to co-infection where the virulence of involved pathogens may be promoted and enhance disease severity, we investigated how K. oxytoca affects the adhesion of commonly co-isolated bacteria and vice versa during co-incubation of different biotic and abiotic surfaces. Co-incubation was beneficial for the adhesion of at least one of the two co-cultured strains. K. oxytoca enhanced the adhesion of other enterobacteria strains to polystyrene and adhered more efficiently to bladder or lung epithelial cell lines in the presence of most enterobacteria strains and S. aureus. This effect was accompanied by bacterial coaggregation mediated by carbohydrate-protein interactions occurring between bacteria. These interactions occur only in sessile, but not planktonic populations, and depend on the features of the surface. The data are of particular importance for the risk assessment of the urinary and respiratory tract infections caused by K. oxytoca, including those device-associated. In this paper, we present the first report on K. oxytoca ability to acquire increased adhesive capacities on epithelial cells through interactions with common causal agents of urinary and respiratory tract infections.

Calcium-dependent reversible coaggregation activity of C-reactive protein and M-ficolin

C-reactive protein (CRP) and M-ficolin are the pattern recognition proteins of the innate immune system. In this report, a mixture of CRP and M-ficolin reversibly co-aggregated in a calcium-dependent manner. This coaggregation was enhanced at low pH (6.5) or low salt (35 mM NaCl) concentrations. The co-aggregate was dissolved by adding EDTA and reformed by adding calcium. The M-ficolin fibrinogen-like domain (FD1), the ligand-binding domain of M-ficolin, also showed calcium-dependent coaggregation with CRP, indicating that reversible coaggregation is caused by CRP interacting with FD1. Interestingly, adding phosphocholine (PC), the ligand of CRP, to a CRP-FD1 mixture abolished the reversible coaggregation activity. PC also inhibited the interaction between CRP and FD1. These results indicate that CRP retains PC-binding activity in the coaggregation state and that FD1 binds specifically to the PC-binding site on CRP but does not fully occupy the five PC-binding sites on a CRP pentamer as judged by SDS-PAGE analysis of precipitates. Coaggregation analysis using FD1 mutants showed that FD1 also retains ligand-binding activity in the coaggregation state and that coaggregation requires the trimeric form of FD1. It was also found that modifications to the ligand-binding site of FD1 affect coaggregation efficiency. Although the biological functions of the coaggregation activity of CRP and M-ficolin remain unresolved, the co-aggregates may function as bacteria-trapping particles with affinities for ligands of CRP and M-ficolin. In addition, coaggregation may be involved in CRP deposition in the lesions of several arterial diseases, such as atherosclerosis.

Efficacy of auto-aggregating aerobic denitrifiers with coaggregation traits for bioaugmentation performance in biofilm-formation and nitrogen-removal

To promote efficiency nitrogen-rich wastewater treatment from a sequencing batch biofilm reactor (SBBR), three aerobic denitrifiers (Pseudomonas mendocinaIHB602, Methylobacterium gregansDC-1 and Pseudomonas stutzeriIHB618) with dual-capacities of strong auto-aggregation and high nitrogen removal efficiency were studied. The aggregation index analysis indicated that coaggregation of the three strains co-existed was better when compared with one or two strains grown alone. Optimal coaggregation strains were used to bioaugmente a test reactor (SBBR_T), which exhibited a shorter time for biofilm-formation than uninoculated control reactor (SBBR_C). With different influent ammonia-N loads (150, 200 and 300 mg·L^-1), the average ammonia-N and nitrate-N removal efficiency were all higher than that in SBBR_C, as well as a lower nitrite-N accumulation. Microbial community structure analysis revealed coaggregation strains may successfully colonize in the bioreactor and be very tolerant of high nitrogen concentrations, and contribute to the high efficiency of inorganic nitrogen-removal and biofilm-formation.

Isolation and characterization of vaginal Lactobacillus spp. in dromedary camels (Camelus dromedarius): in vitro evaluation of probiotic potential of selected isolates

Lactobacillus spp. is one of the beneficial lactic acid producing microbiota in the vagina, which is important for a healthy vaginal environment. However, little is known about vaginal Lactobacillus in dromedary camels (Camelus dromedarius). Therefore, this study aimed to isolate vaginal lactic acid bacteria (LAB) in dromedary camels and to study the probiotic potential of selected isolates. A total of 75 vaginal swabs were collected from pluriparous, non-pregnant, non-lactating dromedary camels. The LAB were isolated using deMan, Rogosa and Sharpe broth and agar media. Suspected LAB isolates were subjected to catalase testing and Gram staining and examined for indole production, nitrate reduction, hemolytic activity, cell surface hydrophobicity, auto- and coaggregation, antibacterial activity and characterized by 16S rRNA amplification and sequencing. Eighteen LABs were isolated from the 75 vaginal swabs. Among the 18 LAB isolates, six were Lactobacillus plantarum, eight were Lactobacillus fermentum, and four were Lactobacillus rhamnosus. None of the LAB isolates was hemolytic and only four LAB were H2O2 producing. The percentage of hydrophobicity ranged from 0% to 49.6%, 0% to 44.3% and 0% to 41.6% for hexadecane, xylene and toluene, respectively. All isolates showed higher (P < 0.05) autoaggregation after 24 h of incubation compared to 4 h. Furthermore, all LAB showed higher coaggregation (P < 0.05) and antimicrobial activity toward Staphylococcus aureus than to Escherichia coli. All LAB isolates were vancomycin resistant and sensitive to streptomycin, erythromycin, kanamycin and chloramphenicol. Only, three LAB isolates were resistant to tetracycline. The dromedary camel vaginal LAB isolates exhibited varying degrees of in vitro probiotic properties tested in this study and showed promising activity against the most common bacterial causes of endometritis in dromedary camels. Further investigation of the in vivo effect of these isolates is warranted.

Amyloid cross-seeding raises new dimensions to understanding of amyloidogenesis mechanism

Hallmarks of most of the amyloid pathologies are surprisingly found to be heterocomponent entities such as inclusions and plaques which contain diverse essential proteins and metabolites. Experimental studies have already revealed the occurrence of coaggregation and cross-seeding during amyloid formation of several proteins and peptides, yielding multicomponent assemblies of amyloid nature. Further, research reports on the co-occurrence of more than one type of amyloid-linked pathologies in the same individual suggest the possible cross-talk among the disease related amyloidogenic protein species during their amyloid growth. In this review paper, we have tried to gain more insight into the process of coaggregation and cross-seeding during amyloid aggregation of proteins, particularly focusing on their relevance to the pathogenesis of the protein misfolding diseases. Revelation of amyloid cross-seeding and coaggregation seems to open new dimensions in our mechanistic understanding of amyloidogenesis and such knowledge may possibly inspire better designing of anti-amyloid therapeutics.

Coaggregation of bacterial communities in aerobic granulation and its application on the biodegradation of sulfolane

Aerobic granulation is regarded as the future technology for wastewater treatment that can replace conventional activated sludge. In this study, two approaches of forming sulfolane degrading aerobic granules (SDAG) were successfully developed and evaluated. These include adaptation of pre-grown granules to sulfolane environment and coaggregation of pre-grown granules with bacterial culture native to sulfolane contaminated site. The adaption method required a longer period to form robust SDAG compared to coaggregation method where degradation of sulfolane was observed within 24 h. Electronic images revealed dominant filamentous bacteria on the surface of granules while DNA analysis unveiled the complexity of the dynamic change of microbial community during aerobic granule formation. The rate of sulfolane degradation by coaggregated granules reduced as the concentration of carbon source increased, nevertheless, the rate increased with increased biomass. In addition, the presence of co-contaminants can slightly impact the ability of newly cultivated granules to degrade sulfolane. Finally, the stability and settleability of the new aerobic granules was investigated under different environmental conditions. About 30% of the aerobic granules were lost after 14 d of operation without any continuous supply of carbon sources. The surviving SDAGs continued to display an intact structure coupled with good settleability.

The Oral Bacterium Fusobacterium nucleatum Binds Staphylococcus aureus and Alters Expression of the Staphylococcal Accessory Regulator sarA

Staphylococcus aureus, an opportunistic pathogen member of the nasal and skin microbiota, can also be found in human oral samples and has been linked to infectious diseases of the oral cavity. As the nasal and oral cavities are anatomically connected, it is currently unclear whether S. aureus can colonize the oral cavity and become part of the oral microbiota, or if its presence in the oral cavity is simply transient. To start addressing this question, we assessed S. aureus ability to directly bind selected members of the oral microbiota as well as its ability to integrate into a human-derived complex oral microbial community in vitro. Our data show that S. aureus forms aggregates with Fusobacterium nucleatum and Porphyromonas gingivalis and that it can incorporate into the human-derived in vitro oral community. Further analysis of the F. nucleatum-S. aureus interaction revealed that the outer-membrane adhesin RadD is partially involved in aggregate formation and that the RadD-mediated interaction leads to an increase in expression of the staphylococcal global regulator gene sarA. Our findings lend support to the notion that S. aureus can become part of the complex microbiota of the human mouth, which could serve as a reservoir for S. aureus. Furthermore, direct interaction with key members of the oral microbiota could affect S. aureus pathogenicity contributing to the development of several S. aureus associated oral infections.

Interactions between oral commensal Candida and oral bacterial communities in immunocompromised and healthy children

Candida species are usually found as commensal microorganisms in the oral cavity of healthy people. During chemotherapy, cytostatic drugs lead to depletion of the oral flora with the emergence of a dominant bacterial species. The transition from commensal to pathogenic state, further associated with yeast colonization and oral mucositis implies a replacement of the dominant microorganism by Candida albicans. This process goes plausibly through cooperation between C. albicans and bacteria. This study focused on the first step of cooperation between microorganisms isolated from the same oral flora either of leukemic or healthy children. C. albicans isolated from 8/20 children were cultured to display their noninvasive blastosporic yeast form and mixed with their dominant bacteria to study the capacity of planktonic aggregation and the early state of biofilm formation. None of the dominant bacteria opposed the presence of yeast, on the contrary, an interesting cooperation was observed. This behavior is apparently different from that observed when mixing the type strains. In fact, three mutated C. albicans strains display, by their spontaneous ability to form filament, enhanced risks of virulence for leukemic ill carriers. Despite such risks, neither oral nor systemic pathology were observed in ill patients probably because the study was conducted during the first course of chemotherapy and Candida colonization is related to the number of chemotherapeutic cycles. The presence of C. albicans during the initial cycle represents, by its ability to interact with oral bacteria, an actual threat for further cures.

TAR DNA-Binding Protein 43 and Disrupted in Schizophrenia 1 Coaggregation Disrupts Dendritic Local Translation and Mental Function in Frontotemporal Lobar Degeneration

BACKGROUND

Neurodegenerative diseases involving protein aggregation often accompany psychiatric symptoms. Frontotemporal lobar degeneration (FTLD) associated with TAR DNA-binding protein 43 (TDP-43) aggregation is characterized by progressive neuronal atrophy in frontal and temporal lobes of cerebral cortex. Furthermore, patients with FTLD display mental dysfunction in multiple behavioral dimensions. Nevertheless, their molecular origin for psychiatric symptoms remains unclear.

METHODS

In FTLD neurons and mouse models with TDP-43 aggregates, we examined coaggregation between TDP-43 and disrupted in schizophrenia 1 (DISC1), a key player in the pathology of mental conditions and its effects on local translation in dendrites and psychiatric behaviors. The protein coaggregation and the expression level of synaptic proteins were also investigated with postmortem brains from patients with FTLD (n = 6).

RESULTS

We found cytosolic TDP-43/DISC1 coaggregates in brains of both FTLD mouse model and patients with FTLD. At the mechanistic levels, the TDP-43/DISC1 coaggregates disrupted the activity-dependent dendritic local translation through impairment of translation initiation and, in turn, reduced synaptic protein expression. Behavioral deficits detected in FTLD model mice were ameliorated by exogenous DISC1 expression.

CONCLUSIONS

Our findings reveal a novel role of the aggregate-prone TDP-43/DISC1 protein complex in regulating local translation, which affects aberrant behaviors relevant to multiple psychiatric dimensions.

A Filter Retardation Assay Facilitates the Detection and Quantification of Heat-Stable, Amyloidogenic Mutant Huntingtin Aggregates in Complex Biosamples

N-terminal mutant huntingtin (mHTT) fragments with pathogenic polyglutamine (polyQ) tracts spontaneously form stable, amyloidogenic protein aggregates with a fibrillar morphology. Such structures are detectable in brains of Huntington's disease (HD) patients and various model organisms, suggesting that they play a critical role in pathogenesis. Heat-stable, fibrillar mHTT aggregates can be detected and quantified in cells and tissues using a denaturing filter retardation assay (FRA). Here, we describe step-by-step protocols and experimental procedures for the investigation of mHTT aggregates in complex biosamples using FRAs. The methods are illustrated with examples from studies in cellular, transgenic fly, and mouse models of HD, but can be adapted for any disease-relevant protein with amyloidogenic polyQ tracts.

Nicotine Upregulates Coaggregation of Candida albicans and Streptococcus mutans

PURPOSE

Denture stomatitis is a condition of painless inflammation of denture-bearing mucosa. Reports indicate that nicotine, the major psychoactive ingredient in tobacco, increases growth of Streptococcus mutans and Candida albicans in denture biofilm. The purpose of this study was to determine the in vitro effects of nicotine on coaggregation of C. albicans with S. mutans.

MATERIAL AND METHODS

C. albicans strain ATCC 10231, S. mutans strain UA159 (ATTC 700610), and nicotine dilutions (ranging from 0 to 32 mg/ml) were used for this study. Both microorganisms were grown for 24 hours in dilutions of nicotine (0 to 32 mg/ml) made in tryptic soy broth (TSB) or TSB supplemented with 1% sucrose (TSBS; S. mutans) or yeast peptone dextrose broth (YPD; C. albicans). Suspensions of the nicotine-treated cells were prepared, mixed together and incubated for up to 24 hours to determine if there was an increase in coaggregation of nicotine-treated cells compared to the no nicotine control cells. Qualitative analysis of coaggregation was performed using a visual aggregation assay and light microscopic observation. A spectrophotometric assay was used to provide a quantitative analysis of the coaggregation.

RESULTS

The visual aggregation assay indicated a significant increase in coaggregation between C. albicans and S. mutans with increasing incubation time (0 to 24 hours) and nicotine concentrations (0 to 4 mg/ml). Microbial growth in nicotine at 4 mg/ml demonstrated a significant increase in coaggregation after 24 hours of incubation. The numbers of coaggregated S. mutans/C. albicans cells exhibited a significant increase with incubation time and nicotine concentrations when the samples were examined microscopically. More coaggregation of S. mutans and C. albicans was observed with incubation time and increased nicotine compared to the 0 mg/ml nicotine group. There was a noticeable increase of coaggregation when cells were grown in TSBS compared to TSB. Absorbance of nicotine-treated cells (0.25 to 4 mg/ml) exhibited a decrease in values compared to 0 mg/ml at 0 hours of incubation, confirming increased coaggregation.

CONCLUSION

These results demonstrated the effect of nicotine in increasing the coaggregation of S. mutans with C. albicans. Coaggregation increased with incubation time and nicotine concentration. Coaggregation was increased with S. mutans grown in TSBS compared to TSB, suggesting that growth in sucrose media leads to an increase in receptors responsible for coaggregation.

Effects of surface reaction-type pre-reacted glass ionomer on oral biofilm formation of Streptococcus gordonii

Streptococcus gordonii, a bacterium involved in the initial colonization of tooth surfaces, contributes to dental biofilm formation and is an important cause of infective endocarditis. This study aimed to investigate the influence of surface reaction-type pre-reacted glass ionomer (S-PRG) filler on oral bacterial growth and aggregation of S. gordonii. The effect of various concentrations of S-PRG eluate on the growth and the biofilm formation of S. gordonii and other oral microorganisms (Streptococcus mutans, Streptococcus oralis, Lactobacillus acidophilus, and Candida albicans) was assessed. In addition, the effect of S-PRG eluate on coaggregation of S. gordonii with both S. oralis and Fusobacterium nucleatum was assessed. The effect of S-PRG eluate treatment on autoaggregation of S. gordonii was also evaluated. Our results indicate that S-PRG eluate treatment reduced both for the growth and for biofilm of all organisms in a dose-dependent manner. Coaggregation of S. gordonii with both S. oralis and F. nucleatum was inhibited by S-PRG eluate, whereas autoaggregation of S. gordonii increased at certain concentrations of S-PRG eluate. These results indicate that the S-PRG filler possesses antimicrobial activity that is mediated by inhibiting growth and biofilm of oral microorganisms, and by suppressing coaggregation of S. gordonii. In addition, these findings indicate that coaggregation of S. gordonii with other bacteria is inhibited by increased autoaggregation of S. gordonii.

Community interactions of oral streptococci

It is now clear that the most common oral diseases, dental caries and periodontitis, are caused by mixed-species communities rather than by individual pathogens working in isolation. Oral streptococci are central to these disease processes since they are frequently the first microorganisms to colonize oral surfaces and they are numerically the dominant microorganisms in the human mouth. Numerous interactions between oral streptococci and other bacteria have been documented. These are thought to be critical for the development of mixed-species oral microbial communities and for the transition from oral health to disease. Recent metagenomic studies are beginning to shed light on the co-occurrence patterns of streptococci with other oral bacteria. Refinements in microscopy techniques and biofilm models are providing detailed insights into the spatial distribution of streptococci in oral biofilms. Targeted genetic manipulation is increasingly being applied for the analysis of specific genes and networks that modulate interspecies interactions. From this work, it is clear that streptococci produce a range of extracellular factors that promote their integration into mixed-species communities and enable them to form social networks with neighboring taxa. These "community integration factors" include coaggregation-mediating adhesins and receptors, small signaling molecules such as peptides or autoinducer-2, bacteriocins, by-products of metabolism including hydrogen peroxide and lactic acid, and a range of extracellular enzymes. Here, we provide an overview of various types of community interactions between oral streptococci and other microorganisms, and we consider the possibilities for the development of new technologies to interfere with these interactions to help control oral biofilms.