Assessing the performance of polyphosphate accumulating organisms in a full-scale side-stream enhanced biological phosphorous removal.

Phosphorous (P) removal in wastewater treatment is essential to prevent eutrophication in water bodies. Side-stream enhanced biological phosphorous removal (S2EBPR) is utilized to improve biological P removal by recirculating internal streams within a side-stream reactor to generate biodegradable carbon (C) for polyphosphate accumulating organisms (PAOs). In this study, a full-scale S2EBPR system in a water resource recovery facility (WRRF) was evaluated for 5 months. Batch experiments revealed a strong positive correlation (r = 0.91) between temperature and C consumption rate (3.56-8.18 mg-COD/g-VSS/h) in the system, with temperature ranging from 14°C to 18°C. The anaerobic P-release to COD-uptake ratio decreased from 0.93 to 0.25 mg-P/mg-COD as the temperature increased, suggesting competition between PAOs and other C-consumers, such as heterotrophic microorganisms, to uptake bioavailable C. Microbial community analysis did not show a strong relationship between abundance and activity of PAO in the tested WRRF. An assessment of the economic feasibility was performed to compare the costs and benefits of a full scale WRRF with and without implementation of the S2EBPR technology. The results showed the higher capital costs required for S2EBPR were estimated to be compensated after 5 and 11 years of operation, respectively, compared to chemical precipitation and conventional EBPR. The results from this study can assist in the decision-making process for upgrading a conventional EBPR or chemical P removal process to S2EBPR. PRACTITIONER POINTS: Implementation of S2EBPR presents adaptable configurations, exhibiting advantages over conventional setups in addressing prevalent challenges associated with phosphorous removal. A full-scale S2EBPR WRRF was monitored over 5 months, and activity tests were used to measure the kinetic parameters. The seasonal changes impact the kinetic parameters of PAOs in the S2EBPR process, with elevated temperatures raising the carbon demand. PAOs abundance showed no strong correlation with their activity in the full-scale S2EBPR process in the tested WRRF. Feasibility assessment shows that the benefits from S2EBPR operation can offset upgrading costs from conventional BPR or chemical precipitation.

Anode amendment with kaolin and activated carbon increases electricity generation in a microbial fuel cell.

The bacterial anode is a key factor for microbial fuel cell (MFC) performance. This study examined the potential of kaolin (fine clay) to enhance bacteria and conductive particle attachment to the anode. The bio-electroactivity of MFCs based on a carbon-cloth anode modified by immobilization with kaolin, activated carbon, and Geobacter sulfurreducens (kaolin-AC), with only kaolin (kaolin), and a bare carbon-cloth (control) anodes were examined. When the MFCs were fed with wastewater, the MFCs based on the kaolin-AC, kaolin, and bare anodes produced a maximum voltage of 0.6 V, 0.4 V, and 0.25 V, respectively. The maximum power density obtained by the MFC based on the kaolin-AC anode was 1112 mW‧m-2 at a current density of 3.33 A‧m-2, 12% and 56% higher than the kaolin and the bare anodes, respectively. The highest Coulombic efficiency was obtained by the kaolin-AC anode (16%). The relative microbial diversity showed that Geobacter displayed the highest relative distribution of 64% in the biofilm of the kaolin-AC anode. This result proved the advantage of preserving the bacterial anode exoelectrogens using kaolin. To our knowledge, this is the first study evaluating kaolin as a natural adhesive for immobilizing exoelectrogenic bacteria to anode material in MFCs.

Viable but nonculturable (VBNC) state, an underestimated and controversial microbial survival strategy.

As a unique microbial response to adverse circumstances, the viable but nonculturable (VBNC) state is characterized by the loss of culturability of microbial cells on/in nutrient media that normally support their growth, while maintaining metabolic activity. These cells can resuscitate to a culturable state under suitable conditions. Given the intrinsic importance of the VBNC state and recent debates surrounding it, there is a need to redefine and standardize the term, and to address essential questions such as 'How to differentiate VBNC from other similar terms?' and 'How can VBNC cells be standardly and accurately determined?'. This opinion piece aims at contributing to an improved understanding of the VBNC state and promoting its proper handling as an underestimated and controversial microbial survival strategy.

Mitigation and use of biofilms in space for the benefit of human space exploration.

Biofilms are self-organized communities of microorganisms that are encased in an extracellular polymeric matrix and often found attached to surfaces. Biofilms are widely present on Earth, often found in diverse and sometimes extreme environments. These microbial communities have been described as recalcitrant or protective when facing adversity and environmental exposures. On the International Space Station, biofilms were found in human-inhabited environments on a multitude of hardware surfaces. Moreover, studies have identified phenotypic and genetic changes in the microorganisms under microgravity conditions including changes in microbe surface colonization and pathogenicity traits. Lack of consistent research in microgravity-grown biofilms can lead to deficient understanding of altered microbial behavior in space. This could subsequently create problems in engineered systems or negatively impact human health on crewed spaceflights. It is especially relevant to long-term and remote space missions that will lack resupply and service. Conversely, biofilms are also known to benefit plant growth and are essential for human health (i.e., gut microbiome). Eventually, biofilms may be used to supply metabolic pathways that produce organic and inorganic components useful to sustaining life on celestial bodies beyond Earth. This article will explore what is currently known about biofilms in space and will identify gaps in the aerospace industry's knowledge that should be filled in order to mitigate or to leverage biofilms to the advantage of spaceflight.

Poor Agreement Between Next-Generation DNA Sequencing and Bacterial Cultures in Orthopaedic Trauma Procedures.

BACKGROUND: Next-generation DNA sequencing (NGS) detects bacteria-specific DNA corresponding to the 16S ribosomal RNA gene and can identify bacterial presence with greater accuracy than traditional culture methods. The clinical relevance of these findings is unknown. The purpose of the present study was to compare the results from bacterial culture and NGS in order to characterize the potential use of NGS in orthopaedic trauma patients. METHODS: A prospective cohort study was performed at a single academic, level-I trauma center. Three patient groups were enrolled: (1) patients undergoing surgical treatment of acute closed fractures (presumed to have no bacteria), (2) patients undergoing implant removal at the site of a healed fracture without infection, and (3) patients undergoing a first procedure for the treatment of a fracture nonunion who might or might not have subclinical infection. Surgical site tissue was sent for culture and NGS. The proportions of culture and NGS positivity were compared among the groups. The agreement between culture and NGS results was assessed with use of the Cohen kappa statistic. RESULTS: Bacterial cultures were positive in 9 of 111 surgical sites (110 patients), whereas NGS was positive in 27 of 111 surgical sites (110 patients). Significantly more cases were positive on NGS as compared with culture (24% vs. 8.1%; p = 0.001), primarily in the acute closed fracture group. No difference was found in terms of the percent positivity of NGS when comparing the acute closed fracture, implant removal, and nonunion groups. With respect to bacterial identification, culture and NGS agreed in 73% of cases (κ = 0.051; 95% confidence interval, -0.12 to 0.22) indicating only slight agreement compared with expected chance agreement of 50%. CONCLUSIONS: NGS identified bacterial presence more frequently than culture, but with only slight agreement between culture and NGS. It is possible that the increased frequency of bacterial detection with molecular methods is reflective of biofilm presence on metal or colonization with nonpathogenic bacteria, as culture methods have selection pressure posed by restrictive, artificial growth conditions and there are low metabolic activity and replication rates of bacteria in biofilms. Our data suggest that NGS should not currently substitute for or complement conventional culture in orthopaedic trauma cases with low suspicion of infection. LEVEL OF EVIDENCE: Diagnostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Current and novel diagnostics for orthopedic implant biofilm infections: a review.

Biofilm infections involving orthopedic implants are a global problem. They contribute to severe complications and mortality, as well as increased use of antibiotic treatments and development of antibiotic-resistant microorganisms. More than 1 million hip and knee arthroplasties are performed each year in the United States. These hard-to-treat infections lead to patient distress, increased morbidity, and high financial costs to both patients and healthcare systems. There is a need to improve the diagnosis of such biofilm infections to allow for earlier detection and treatment. Current diagnostics rely on clinical signs for infections such as loss of function, fever, rubor, patient history of the predisposing condition, persisting infection, failure of antibiotic treatment, and documentation of antibiotic failure. Below, we present a framework which outlines the data gaps in the conventional laboratory techniques used in clinical diagnostics; we also discuss promising novel diagnostic methods which are currently used solely in research. It is critical to assess these novel infection diagnostic techniques and address the data gaps and clinical hesitance preventing application in a clinical setting. Additionally, the combination of conventional and novel diagnostic technologies would streamline the diagnostic process of biofilm infections associated with orthopedic implants.

Impact of pmrA on Cronobacter sakazakii planktonic and biofilm cells: A comprehensive transcriptomic study.

Cronobacter sakazakii is an emerging opportunistic foodborne pathogen causing rare but severe infections in neonates. Furthermore, the formation of biofilm allows C. sakazakii to persist in different environments. We have demonstrated that the mutator phenotype ascribed to deficiency of the pmrA gene results in more biomass in the first 24 h but less during the post maturation stage (7-14 d) compared with BAA 894. The present study aimed to investigate the regulatory mechanism modulating biofilm formation due to pmrA mutation. The transcriptomic analyses of BAA 894 and s-3 were performed by RNA-sequencing on planktonic and biofilm cells collected at different time points. According to the results, when comparing biofilm to planktonic cells, expression of genes encoding outer membrane proteins, lysozyme, etc. were up-regulated, with LysR family transcriptional regulators, periplasmic proteins, etc. down-regulated. During biofilm formation, cellulose synthase operon genes, flagella-related genes, etc. played essential roles in different stages. Remarkably, pmrA varies the expression of a number of genes related to motility, biofilm formation, and antimicrobial resistance, including srfB, virK, mviM encoding virulence factor, flgF, fliN, etc. encoding flagellar assembly, and marA, ramA, etc. encoding AraC family transcriptional regulators in C. sakazakii. This study provides valuable insights into transcriptional regulation of C. sakazakii pmrA mutant during biofilm formation.

Colonization and growth of dehalorespiring biofilms on carbonaceous sorptive amendments.

Removal of polychlorinated biphenyls (PCBs) from contaminated sediments is a priority due to accumulation in the food chain. Recent success with reduction of PCB bioavailability due to adsorption onto activated carbon led to the recognition of in situ treatment as a remediation approach. In this study, reduced bioavailability and subsequent break-down of PCBs in dehalorespiring biofilms was investigated using Dehalobium chlorocoercia DF1. DF1 formed a patchy biofilm ranging in thickness from 3.9 to 6.7 µm (average 4.6 ± 0.87 µm), while the biofilm coverage varied from 5.5% (sand) to 20.2% (activated carbon), indicating a preference for sorptive materials. Quantification of DF1 biofilm bacteria showed 1.2-15.3 × 109 bacteria per gram of material. After 22 days, coal activated carbon, bone biochar, polyoxymethylene, and sand microcosms had dechlorinated 73%, 93%, 100%, and 83%, respectively. These results show that a biofilm-based inoculum for bioaugmentation of PCBs in sediment can be an efficient approach.

Microbial phyto-power systems - A sustainable integration of phytoremediation and microbial fuel cells.

Constructed wetland microbial fuel cells (CW-MFCs) or phyto-power systems are integrated bioelectrochemical systems (BES) that can sustainably harvest electricity from the anaerobic respiration of rhizospheric bacteria. This integration of techniques shows a promise in phytoremediation of wastewater along with bioenergy generation. In CW-MFCs, electrons harvested in anaerobic respiration of bacteria proliferating in the rhizospheric zone are electrochemically coupled with electron acceptors at the aerobic cathode submersed in water. Use of indigenous non-food plants in CW-MFCs has gained increasing interest primarily due to high yield of biomass that can be applied for other bioenergy purposes and bioaccumulation of pollutants. Furthermore, CW-MFCs can provide other benefits such as wastewater treatment, carbon dioxide assimilation, power generation and air purification. Microbial interaction with plant roots (rhizosphere), isolated species from the phyto-systems, with soil particles and pollutants are reviewed in this paper. In addition, successful applications of CW-MFCs are discussed with focus on power generation, the role of plant-microbe interactions as well as evaluating the critical operational parameters and their effect on power generation output efficiency.

Positive Matrix Factorization analysis shows dechlorination of polychlorinated biphenyls during domestic wastewater collection and treatment.

Polychlorinated biphenyls (PCBs) are persistent, toxic and bioaccumulative pollutants. One of the few pathways via which they break down is microbial dechlorination, which has been shown to occur in sewers. Questions remain about where within sewers this process takes place and which conditions encourage dechlorination. These issues were examined using a large data set on PCBs in influent and effluents from a main and bypass outfall from a wastewater treatment facility in the Mid-Atlantic region of the USA. A data set containing 64 chromatographic peaks representing 103 PCB congeners measured in 74 whole water samples was analyzed by Positive Matrix Factorization (PMF). PMF resolved four factors, three of which represented Aroclors 1242, 1254, and 1260. The remaining factor represented an advanced dechlorination regime of PCBs characterized by high proportions of PCBs 4 and 19 and comprised about 35% of the PCBs in the treated effluent, among the highest levels of dechlorination observed in previous studies. Concentrations of dechlorination products were not correlated with total suspended solids, indicating they were mostly dissolved and explaining the poor removal via sedimentation during the treatment process. The factors representing Aroclors were positively correlated with total influent flow, but the dechlorination signal was not, suggesting that the dechlorination signal arises from different locations and/or processes than the Aroclors. Even though treatment and dechlorination reduced the dioxin-like toxicity of the PCB mixture, this effect might be offset by the incomplete removal of dechlorination products.

Elimination of Bloodstream Infections Associated with Candida albicans Biofilm in Intravascular Catheters.

Intravascular catheters are among the most commonly inserted medical devices and they are known to cause a large number of catheter related bloodstream infections (BSIs). Biofilms are associated with many chronic infections due to the aggregation of microorganisms. One of these organisms is the fungus Candida albicans. It has shown to be one of the leading causes of catheter-related BSIs. The presence of biofilm on intravascular catheters provide increased tolerance against antimicrobial treatments, thus alternative treatment strategies are sought. Traditionally, many strategies, such as application of combined antimicrobials, addition of antifungals, and removal of catheters, have been practiced, but they were not successful in eradicating BSIs. Since these fungal infections can result in significant morbidity, mortality, and increased healthcare cost, other promising preventive strategies, including antimicrobial lock therapy, chelating agents, alcohol, and biofilm disruptors, have been applied. In this review, current success and failure of these new approaches, and a comparison with the previous strategies are discussed in order to understand which preventative treatment is the most effective in controlling the catheter-related BSIs.

Phylogenetic and functional diversity of bacteria in biofilms from metal surfaces of an alkaline district heating system.

District heating systems (DHS) are extreme aqueous environments characterized by high temperatures, high pH (9.5-10.0), and low nutrient availability. Culture-independent and culture-dependent techniques showed that DHS may nevertheless harbour geno- and phenotypically diverse bacterial biofilm communities. Approximately 50% of the cells in biofilms growing on mild steel coupons in rotortorque reactors connected to the return line (40 degrees C) of a Danish DHS were detectable by FISH analysis and thus were probably metabolically active. A bacterial 16S rRNA gene clone library generated from the biofilms was dominated by proteobacterial phylotypes (closely related to known aerobic species) and by phylotypes affiliated to the anaerobic class Clostridia. Anoxic enrichment cultures derived from biofilms primarily contained 16S rRNA gene and dsrAB (encoding major subunits of dissimilatory sulfite reductase) phylotypes affiliated to the latter class. Alkalitolerant and neutrophilic anaerobic bacteria were isolated from the DHS, including novel Gram-positive and deltaproteobacterial sulfate-reducers and sulfite-reducers constituting novel Gram-positive lineages. In total, 39 distinct 16S rRNA gene phylotypes representing ten classes were identified. The detection of several alkalitolerant, sulfide-producing, and, thus, potentially biocorrosive species underlines the need to maintain a high water quality in the DHS in order to prevent the proliferation of these species.

In situ studies of the phylogeny and physiology of filamentous bacteria with attached growth.

Among the filamentous bacteria occasionally causing bulking problems in activated sludge treatment plants, three morphotypes with attached microbial growth are common, Eikelboom Type 0041, Type 1851 and Type 1701. A better knowledge of the phylogeny and physiology of these filamentous bacteria is necessary in order to develop control strategies for bulking. In this study we have used a combination of fluorescence in situ hybridization (FISH) and microautoradiography (MAR) to investigate the identity and in situ physiology of the Type 0041-morphotype and its attached bacteria in two wastewater treatment plants. Identification and enumeration of Type 0041 using group-specific 16S rRNA-targeted FISH probes revealed that approximately 15% of the filaments hybridized with a gene probe specific for the TM7 group, a recently recognized major lineage in the bacterial domain. All other filaments morphologically identified as Type 0041 only hybridized to the general bacterial EUB338-probe, indicating that they probably do not belong to commonly isolated bacterial phyla such as the Proteobacteria, Firmicutes, Actinobacteria and Bacteroidetes, for which group-specific probes were used. The phylogenetic heterogeneity of Type 0041 again highlights the inadequacy of a morphology-based classification system. Like the filaments, most of the attached microbial cells were not identified beyond their affiliation to the Bacteria using the group-specific FISH probes. However, several different bacterial phyla were represented in the identified fraction suggesting that the attached microorganisms are phylogenetically diverse. The study of the in situ physiology of Type 0041 using MAR-FISH revealed that both the filaments and the attached bacteria on Type 0041 were versatile in the use of organic substrates and electron acceptors. It was observed that all Type 0041 could consume glucose, but none of the filaments were able to consume acetate under any conditions tested, in contrast to some of the attached bacteria. No significant physiological differences were found between TM7-positive and TM7-negative Type 0041 filaments, and only minor differences were observed between the two treatment plants tested. These are the first data on the physiology of the almost entirely uncharacterized TM7 phylum and show that TM7 filamentous bacteria can uptake carbon substrates under aerobic and anaerobic conditions.