Search

Pure (single) cultures of microorganisms and mixed microbial communities (microbiomes) have been important for centuries in providing renewable energy, clean water and food products to human society and will continue to play a crucial role to pursue the Sustainable Development Goals. To use microorganisms effectively, microbial engineered processes require adequate control. Microbial communities are shaped by manageable deterministic processes, but also by stochastic processes, which can promote unforeseeable variations and adaptations. Here, we highlight the impact of stochasticity in single culture and microbiome engineering. First, we discuss the concepts and mechanisms of stochasticity in relation to microbial ecology of single cultures and microbiomes. Second, we discuss the consequences of stochasticity in relation to process performance and human health, which are reflected in key disadvantages and important opportunities. Third, we propose a suitable decision tool to deal with stochasticity in which monitoring of stochasticity and setting the boundaries of stochasticity by regulators are central aspects. Stochasticity may give rise to some risks, such as the presence of pathogens in microbiomes. We argue here that by taking the necessary precautions and through clever monitoring and interpretation, these risks can be mitigated.

Novel application of bio-Pd NPs

Lime-based binders, while historically significant, exhibit low strength and slow hardening, which has led to its replacement by cement. Hardening in lime-based materials occurs primarily through carbonation, whereby Ca(OH)2 reacts with atmospheric CO2 and produces CaCO3 cement. This study explores using bacterial additives to accelerate lime hardening by producing extra CO2. Three bacterial species were isolated and grown in liquid media. In a closed container, lime-mortar specimens were indirectly exposed to a cotton soaked in either bacterial suspension or water. Thermogravimetric analysis after 7 and 14 days indicated increased carbonation in cubes incubated with bacterial suspension, but not significantly. Subsequently, one bacterial suspension was mixed directly with lime. Progression of carbonation was tested with phenolphthalein and after 7, 14 and 21 days faster carbonation was seen in bacteria-containing pastes than those with only culture media. Overall, bacteria can carbonate lime materials but further optimization is needed for practical application.

Background: Periodontal diseases are associated with dysbiosis in the oral microbial communities. Managing oral biofilms is therefore key for preventing these diseases. Management protocols often include over‐the‐counter antimicrobial mouth rinses, which lack data on their effects on the oral microbiome's ecology, bacterial composition, metabolic activity, and dysbiosis resilience. This study examined the efficacy of antimicrobial mouth rinses to halt dysbiosis in in vitro oral biofilms under periodontitis‐simulating conditions. Methods: Multispecies oral biofilms were grown on hydroxyapatite discs (HADs) and rinsed daily with one of six mouth rinses. Positive and negative controls were included. After three rinses, biofilms were analyzed with viability quantitative polymerase chain reaction and visualized using scanning electron microscopy. Supernatants of rinsed biofilms were used for metabolic activity analysis. In addition, human oral keratinocytes were exposed to rinsed biofilms to assess their inflammatory response. All outputs were analyzed for correlation using Spearman coefficient. Results: Product‐related changes were observed in the rinsed biofilms. Three of the six tested mouth rinses could significantly prevent dysbiosis with ≥30% reduction in pathobiont abundance relative to the control. These biofilms had lower metabolic activity, and the exposed human oral keratinocyte produced less interleukin‐8. Interleukin‐8 production correlated to both pathobiont quantity and the metabolic activity of the biofilms. Conclusion: Some mouth rinses could support biofilm resilience and stop dysbiosis evolution in the biofilm model, with a clear product‐related effect. Such mouth rinses can be considered for patients under maintenance/supportive periodontal therapy to prevent/delay disease recurrence. Others are more useful for different periodontal therapy stages. [ABSTRACT FROM AUTHOR]

Over time, humanity has addressed microbial water contamination in various ways. Historically, individuals resorted to producing beer to combat the issue. Fast forward to the 19th century, and we witnessed a scientific approach by Robert Koch. His groundbreaking gelatine plating method aimed to identify and quantify bacteria, with a proposed limit of 100 colony‐forming units per millilitre (CFU/mL) to avoid Cholera outbreaks. Despite considerable advancements in plating techniques through experimentation with media compositions and growth temperatures, the reliance on a century‐old method for water safety remains the state‐of‐the‐art. Even though most countries succeed in producing qualitative water at the end of the production centres, it is difficult to control, and guarantee, the same quality during distribution. Rather than focusing solely on specific sampling points, we propose a holistic examination of the entire water network to ensure comprehensive safety. Current practices leave room for uncertainties, especially given the low concentrations of pathogens. Innovative methods like flow cytometry and flow cytometric fingerprinting offer the ability to detect changes in the microbiome of drinking water. Additionally, molecular techniques and emerging sequencing technologies, such as third‐generation sequencing (MinION), mark a significant leap forward, enhancing detection limits and emphasizing the identification of unwanted genes rather than the unwanted bacteria/microorganisms itself. Over the last decades, there has been the realization that the drinking water distribution networks are complex ecosystems that, beside bacteria, comprise of viruses, protozoans and even isopods. Sequencing techniques to find eukaryotic DNA are necessary to monitor the entire microbiome of the drinking water distribution network. Or will artificial intelligence, big data and machine learning prove to be the way to go for (microbial) drinking water monitoring? In essence, it is time to transcend century‐old practices and embrace modern technologies to ensure the safety of our drinking water from production to consumption. [ABSTRACT FROM AUTHOR]

The negative diversity‐invasion relationship observed in microbial invasion studies is commonly explained by competition between the invader and resident populations. However, whether this relationship is affected by invader‐resident cooperative interactions is unknown. Using ecological and mathematical approaches, we examined the survival and functionality of Aminobacter niigataensis MSH1 to mineralize 2,6‐dichlorobenzamide (BAM), a groundwater micropollutant affecting drinking water production, in sand microcosms when inoculated together with synthetic assemblies of resident bacteria. The assemblies varied in richness and in strains that interacted pairwise with MSH1, including cooperative and competitive interactions. While overall, the negative diversity‐invasion relationship was retained, residents engaging in cooperative interactions with the invader had a positive impact on MSH1 survival and functionality, highlighting the dependency of invasion success on community composition. No correlation existed between community richness and the delay in BAM mineralization by MSH1. The findings suggest that the presence of cooperative residents can alleviate the negative diversity‐invasion relationship. [ABSTRACT FROM AUTHOR]

As an alternative to the usage of axenic bacteria to achieve microbially induced calcium carbonate precipitation (MICP), this study evaluates the usage of two non-axenic biomasses as self-healing agents. A fungi-based consortium (Yeast) and heterotrophic nitrifiers (HTN) were harvested from the incubation of agricultural side streams. The characteristics of the two biomasses were identified through flow cytometry, total suspended solids and volatile suspended solids tests. The incorporation of the biomasses into concrete was evaluated in terms of compressive strength, flow and healing ability. Self-healing ability was analyzed through microscope imaging on prismatic (60x60x220 mm) samples. Cracks were induced with a three-point bending test where the widths were controlled with an LVDT sensor. A curing period of 56 days was applied to the samples and visual inspection was conducted at the start and end of the healing period with an optical microscope. Results compare and discuss the differing effects of active and autoclaved biomasses on the concrete properties and crack closure.

The capacity of hydrated lime to reabsorb CO2 as it hardens has made it a desirable replacement for cement to produce mortars with an overall lower environmental footprint. Still, research into lime-cement formulations remains limited, especially when it comes to their self-healing capacity. Some studies show that hydrated lime can improve self-healing in cement mixes, but addition rates are low. Here we present how high lime-cement ratios influence the self-healing capacity of lime mortars. Four mixes of increasing lime-cement ratios were cracked with tensile loading and placed under 1 hour wet, 23 hours dry cycles to stimulate self-healing. The mix design of 50 % lime-50 % cement volume (L50C50) showed self-healing abilities and was tested against a pure cement mixture (L0C100). Microscopy and water flow tests were performed at a cracking age of 7 days and then again after 28 days of healing in three regimes. Overall, submersion was the best healing regime for both L0C100 and L50C50 and crack self-healing was close to total (100 ± 1 % and 98 ± 6 %, respectively). Nevertheless, the water flow tests show that self-healing in L50C50 was in fact less efficient than that of the L0C100, achieving a 39 ± 21 % reduction in water flow versus 86 ± 11 %.