Microbial Growth
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2022 ◽  
Vol 12 ◽  
Author(s):  
Jörg S. Deutzmann ◽  
Grace Callander ◽  
Wenyu Gu ◽  
Albert L. Müller ◽  
Alexandra L. McCully ◽  
...  

Optical density (OD) measurement is the gold standard to estimate microbial cell density in aqueous systems. Recording microbial growth curves is essential to assess substrate utilization, gauge sensitivity to inhibitors or toxins, or determine the perfect sampling point. Manual sampling for cuvette-photometer-based measurements can cause disturbances and impact growth, especially for strictly anaerobic or thermophilic microbes. For slow growing microbes, manual sampling can cause data gaps that complicate analysis. Online OD measurement systems provide a solution, but are often expensive and ill-suited for applications such as monitoring microbial growth in custom or larger anaerobic vessels. Furthermore, growth measurements of thermophilic cultures are limited by the heat sensitivity of complex electronics. Here, we present two simple, low-cost, self-assembled photometers—a “TubeOD” for online measurement of anaerobic and thermophilic cultures in Hungate tubes and a “ClampOD” that can be attached to virtually any transparent growth vessel. Both OD-meters can be calibrated in minutes. We detail the manufacturing and calibration procedure and demonstrate continuous acquisition of high quality cell density data of a variety of microbes, including strict anaerobes, a thermophile, and gas-utilizing strains in various glassware. When calibrated and operated within their detection limits (ca. 0.3–90% of the photosensor voltage range), these self-build OD-meters can be used for continuous measurement of microbial growth in a variety of applications, thereby, simplifying and enhancing everyday lab operations.


2022 ◽  
Vol 12 ◽  
Author(s):  
Siva Kumar Malka ◽  
Me-Hea Park

Maintaining microbial safety and quality of fresh fruits and vegetables are a global concern. Harmful microbes can contaminate fresh produce at any stage from farm to fork. Microbial contamination can affect the quality and shelf-life of fresh produce, and the consumption of contaminated food can cause foodborne illnesses. Additionally, there has been an increased emphasis on the freshness and appearance of fresh produce by modern consumers. Hence, disinfection methods that not only reduce microbial load but also preserve the quality of fresh produce are required. Chlorine dioxide (ClO2) has emerged as a better alternative to chlorine-based disinfectants. In this review, we discuss the efficacy of gaseous and aqueous ClO2 in inhibiting microbial growth immediately after treatment (short-term effect) versus regulating microbial growth during storage of fresh produce (long-term effect). We further elaborate upon the effects of ClO2 application on retaining or enhancing the quality of fresh produce and discuss the current understanding of the mode of action of ClO2 against microbes affecting fresh produce.


Author(s):  
Sanne Johansson ◽  
Kristin Balksten ◽  
Paulien Brigitte Strandberg-de Bruijn

Microbial growth often thrives in humid conditions, at high relative humidity. Moulds are complex organisms; many types of mould are able to survive strong variations in humidity and temperature, such as those on building façades. For some building materials a critical relative humidity is determined, which functions as a theoretical threshold; at this (or lower) relative humidity microbial growth will likely not occur. Hemp-lime is a building material that consists of hemp shiv (the woody core parts of the hemp stem) and building lime. It is a material that can be used for walls, and even though it has been used for more than 20 years, thusfar little is known about its critical moisture levels for microbial growth. The aim of this research was therefore to determine at what relative humidity microbial growth occurs on carbonated hemp-lime material, and to study if there is a protective influence of a carbonated lime binder on the hemp shiv. The objective was to study microbial growth on hemp shiv, hemp-lime and on hemp with a thin layer of lime at three relative humidity (75 %, 85 % and 95 %) and at two different temperatures (15°C and 23°C); conditions that could occur naturally in a hemp-lime façade exposed to high rain loads in a northern European climate. Hemp shiv seems to have a relatively low resistance to microbial growth, similar to that of wood. However, because the hemp is protected by lime it can withstand much higher relative humidity without microbial growth occurring on the material. The critical moisture level for hemp-lime seemed to occur between 75 and 85 % RH, while the material was completely without microbial growth at 75 % RH. The lime had a protective effect on the hemp and acted as a mould inhibitor, both over time and with varying temperature and humidity.


2022 ◽  
pp. gr.275533.121
Author(s):  
Tyler A Joseph ◽  
Philippe Chlenski ◽  
Aviya Litman ◽  
Tal Korem ◽  
Itsik Pe'er

Patterns of sequencing coverage along a bacterial genome---summarized by a peak-to-trough ratio (PTR)---have been shown to accurately reflect microbial growth rates, revealing a new facet of microbial dynamics and host-microbe interactions. Here, we introduce CoPTR (Compute PTR): a tool for computing PTRs from complete reference genomes and assemblies. Using simulations and data from growth experiments in simple and complex communities, we show that CoPTR is more accurate than the current state-of-the-art, while also providing more PTR estimates overall. We further develop theory formalizing a biological interpretation for PTRs. Using a reference database of 2935 species, we applied CoPTR to a case-control study of 1304 metagenomic samples from 106 individuals with inflammatory bowel disease. We show that growth rates are personalized, are only loosely correlated with relative abundances, and are associated with disease status. We conclude by demonstrating how PTRs can be combined with relative abundances and metabolomics to investigate their effect on the microbiome.


2022 ◽  
Vol 21 (1) ◽  
pp. 137-165
Author(s):  
Agustín G. Yabo ◽  
Jean-Baptiste Caillau ◽  
Jean-Luc Gouzé ◽  
Hidde de Jong ◽  
Francis Mairet

2021 ◽  
Vol 118 (52) ◽  
pp. e2115283118
Author(s):  
Heng Huang ◽  
Salvatore Calabrese ◽  
Ignacio Rodriguez-Iturbe

Soil heterotrophic respiration (Rh) represents an important component of the terrestrial carbon cycle that affects whether ecosystems function as carbon sources or sinks. Due to the complex interactions between biological and physical factors controlling microbial growth, Rh is uncertain and difficult to predict, limiting our ability to anticipate future climate trajectories. Here we analyze the global FLUXNET 2015 database aided by a probabilistic model of microbial growth to examine the ecosystem-scale dynamics of Rh and identify primary predictors of its variability. We find that the temporal variability in Rh is consistently distributed according to a Gamma distribution, with shape and scale parameters controlled only by rainfall characteristics and vegetation productivity. This distribution originates from the propagation of fast hydrologic fluctuations on the slower biological dynamics of microbial growth and is independent of biome, soil type, and microbial physiology. This finding allows us to readily provide accurate estimates of the mean Rh and its variance, as confirmed by a comparison with an independent global dataset. Our results suggest that future changes in rainfall regime and net primary productivity will significantly alter the dynamics of Rh and the global carbon budget. In regions that are becoming wetter, Rh may increase faster than net primary productivity, thereby reducing the carbon storage capacity of terrestrial ecosystems.


2021 ◽  
Vol 4 (1) ◽  
pp. 43
Author(s):  
Reno Susanto ◽  
W Revika ◽  
Irdoni Irdoni

Edible film is a packaging that has the advantage of being easily degraded so that it does not cause environmental problems such as plastic waste which can pollute the environment. Edible film is considered to have good prospects for application in food ingredients, one of which is meat, because meat has a limited shelf life. The addition of antimicrobial ingredients to the edible film in the form of essential oil of basil leaves is useful for reducing microbial growth. The purpose of this study was to make edible films to extend the shelf life of frozen meat, utilize banana peels and durian seeds as the main ingredients for making edible films and use basil essential oil as an antimicrobial agent. The stages of activities carried out in this study included the preparation of raw materials for waste banana peels, durian seeds, and basil leaves. This stage includes the extraction process of each ingredient that produces pectin from banana peels, starch from durian seeds, and essential oil from basil leaves. Furthermore, the making of edible films from these raw materials varied the ratio between the mass of pectin and starch. The formed edible films were analyzed using FTIR, attractiveness test, and microbial growth testing by comparing meat coated with edible film and meat not coated with edible film. The characteristics of the edible film produced are 0.1 mm thick with a tensile strength value of 64.65 MPa - 75.34 MPa and a percent elongation value of 0.318% - 0.36%. The best edible film was produced at a ratio of 4: 1 (pectin: starch) with the addition of antimicrobials which had a film thickness of 0.1 mm with a tensile strength value of 75.34 MPa and 0.35% elongation percent.


2021 ◽  
Vol 9 ◽  
Author(s):  
M. Kästner ◽  
A. Miltner ◽  
S. Thiele-Bruhn ◽  
C. Liang

The organic matter of living plants is the precursor material of the organic matter stored in terrestrial soil ecosystems. Although a great deal of knowledge exists on the carbon turnover processes of plant material, some of the processes of soil organic matter (SOM) formation, in particular from microbial necromass, are still not fully understood. Recent research showed that a larger part of the original plant matter is converted into microbial biomass, while the remaining part in the soil is modified by extracellular enzymes of microbes. At the end of its life, microbial biomass contributes to the microbial molecular imprint of SOM as necromass with specific properties. Next to appropriate environmental conditions, heterotrophic microorganisms require energy-containing substrates with C, H, O, N, S, P, and many other elements for growth, which are provided by the plant material and the nutrients contained in SOM. As easily degradable substrates are often scarce resources in soil, we can hypothesize that microbes optimize their carbon and energy use. Presumably, microorganisms are able to mobilize biomass building blocks (mono and oligomers of fatty acids, amino acids, amino sugars, nucleotides) with the appropriate stoichiometry from microbial necromass in SOM. This is in contrast to mobilizing only nutrients and consuming energy for new synthesis from primary metabolites of the tricarboxylic acid cycle after complete degradation of the substrates. Microbial necromass is thus an important resource in SOM, and microbial mining of building blocks could be a life strategy contributing to priming effects and providing the resources for new microbial growth cycles. Due to the energy needs of microorganisms, we can conclude that the formation of SOM through microbial biomass depends on energy flux. However, specific details and the variability of microbial growth, carbon use and decay cycles in the soil are not yet fully understood and linked to other fields of soil science. Here, we summarize the current knowledge on microbial energy gain, carbon use, growth, decay, and necromass formation for relevant soil processes, e. g. the microbial carbon pump, C storage, and stabilization. We highlight the factors controlling microbial necromass contribution to SOM and the implications for soil carbon use efficiency (CUE) and we identify research needs for process-based SOM turnover modelling and for understanding the variability of these processes in various soil types under different climates.


2021 ◽  
Author(s):  
◽  
Sami Aljohani

<p><b>Methylglyoxal (MGO), which is an ingredient in New Zealand Manuka honey (MH) possesses unique antimicrobial properties against a broad range of bacteria. MGO has been determined to have a low minimum inhibitory concentration against bacteria. This provides a new opportunity to develop the use of this compound as a natural antimicrobial agent to impart such antimicrobial properties to wool textiles. This is the focus and detailed research work of this thesis. Also, its application to paper and polymer surfaces has been investigated briefly.</b></p> <p>Due to their protein-based structure and porosity, woollen textiles provide a hospitable host for the growth of microorganisms. This microbial growth on such textiles can pose an undesirable health risk to humans and can negatively affect textile sales. the textile market. Similarly, microbial growth on other substrates such as walls, floors and various equipment can also pose health risks. There are a number of antimicrobial treatments on the market, but with the move to more natural-based antimicrobial agents, there is an opportunity to capture the natural antimicrobial properties of MH and particularly the active ingredient MGO, as a natural antimicrobial agent in wool textiles and paper and polymer substrates.</p> <p>This research developed a novel approach and methodology to incorporate MH and also MGO itself as an isolated component and antimicrobial agent of MH, into the wool fibres and chemically bonding it to the fibre proteins. This approach commenced with determining the extent of uptake of MH, based on its MGO concentration, and MGO itself into wool fibres. The extent of MH and MGO uptake has been determined with High-Performance Liquid Chromatography (HPLC). This uptake was studied over a range of MH and MGO concentrations and temperatures using loose top wool, yarn and finished wool fabric. An increase in temperature from room temperature up to 80 °C resulted in significantly higher amounts of MGO and MH being absorbed by the wool. Also, higher concentrations of the initial MGO and MH solutions accelerated the uptake rates and resulted in higher uptake amounts. The relatively slow diffusion rate of MGO into the wool necessarily required a long period of time, up to 14 days, for the particular uptake to generally reach the saturation level. The maximum amounts of MH and MGO that were incorporated into wool fibres in this study were 21.2 mg g-1 and 299 mg g-1 wool, respectively.</p> <p>The chemical interactions between MGO and MGO in MH with the wool fibres have been characterised by Fourier-Transform Infrared (FTIR) spectroscopy, Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). FTIR spectra showed that the MGO absorption by the wool changed the intensity of particular peaks between 2,000 and 700 cm-1 characteristic of the wool proteins, and the NH stretching peaks of the wool at 3,270 cm-1. The TGA and DSC analyses showed a thermal stability of the wool after MGO absorption and the likely formation of new bonds, probably H-bonds, between the MGO and the wool. Confirming these findings, the MGOWool and MH-Wool showed a resistance against MGO leaching on washing with water, where less than 1% (relative) of MGO leached out. These results suggest the MGO is likely chemically bound to the wool fibres through hydrogen bonding.</p> <p>The MGO-Wool and also MGO-paper composites produced in a similar way with MGO-Wool, exhibited antimicrobial activities against Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli). The MGO-Wool showed bacteriostatic properties for all composites even after three months of being synthesised. This opens up potential applications for the use of MH and MGO in antimicrobial woollen apparel, medical textiles and bandages.</p> <p>In addition, MGO was incorporated into samples of an acrylic polymer NeoCryl® XK-98 and a polyurethane, Kamthane K-5000, polymer resin, respectively. The interaction of MGO with the respective polymer chains resulted in similar hydrogen bonding between MGO and the polymers. At high MGO concentrations this bonding was confirmed by the presence of a new endothermic peak in the DSC pattern. The addition of MGO also modified the polymer surface and resulted in a more hydrophobic surface with an increased water droplet contact angle of 87.5°. The new polymer compositeswere successfully tested against S. aureus and E. coli microbes and were shown to exhibit antimicrobial properties.</p>


2021 ◽  
Author(s):  
◽  
Sami Aljohani

<p><b>Methylglyoxal (MGO), which is an ingredient in New Zealand Manuka honey (MH) possesses unique antimicrobial properties against a broad range of bacteria. MGO has been determined to have a low minimum inhibitory concentration against bacteria. This provides a new opportunity to develop the use of this compound as a natural antimicrobial agent to impart such antimicrobial properties to wool textiles. This is the focus and detailed research work of this thesis. Also, its application to paper and polymer surfaces has been investigated briefly.</b></p> <p>Due to their protein-based structure and porosity, woollen textiles provide a hospitable host for the growth of microorganisms. This microbial growth on such textiles can pose an undesirable health risk to humans and can negatively affect textile sales. the textile market. Similarly, microbial growth on other substrates such as walls, floors and various equipment can also pose health risks. There are a number of antimicrobial treatments on the market, but with the move to more natural-based antimicrobial agents, there is an opportunity to capture the natural antimicrobial properties of MH and particularly the active ingredient MGO, as a natural antimicrobial agent in wool textiles and paper and polymer substrates.</p> <p>This research developed a novel approach and methodology to incorporate MH and also MGO itself as an isolated component and antimicrobial agent of MH, into the wool fibres and chemically bonding it to the fibre proteins. This approach commenced with determining the extent of uptake of MH, based on its MGO concentration, and MGO itself into wool fibres. The extent of MH and MGO uptake has been determined with High-Performance Liquid Chromatography (HPLC). This uptake was studied over a range of MH and MGO concentrations and temperatures using loose top wool, yarn and finished wool fabric. An increase in temperature from room temperature up to 80 °C resulted in significantly higher amounts of MGO and MH being absorbed by the wool. Also, higher concentrations of the initial MGO and MH solutions accelerated the uptake rates and resulted in higher uptake amounts. The relatively slow diffusion rate of MGO into the wool necessarily required a long period of time, up to 14 days, for the particular uptake to generally reach the saturation level. The maximum amounts of MH and MGO that were incorporated into wool fibres in this study were 21.2 mg g-1 and 299 mg g-1 wool, respectively.</p> <p>The chemical interactions between MGO and MGO in MH with the wool fibres have been characterised by Fourier-Transform Infrared (FTIR) spectroscopy, Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). FTIR spectra showed that the MGO absorption by the wool changed the intensity of particular peaks between 2,000 and 700 cm-1 characteristic of the wool proteins, and the NH stretching peaks of the wool at 3,270 cm-1. The TGA and DSC analyses showed a thermal stability of the wool after MGO absorption and the likely formation of new bonds, probably H-bonds, between the MGO and the wool. Confirming these findings, the MGOWool and MH-Wool showed a resistance against MGO leaching on washing with water, where less than 1% (relative) of MGO leached out. These results suggest the MGO is likely chemically bound to the wool fibres through hydrogen bonding.</p> <p>The MGO-Wool and also MGO-paper composites produced in a similar way with MGO-Wool, exhibited antimicrobial activities against Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli). The MGO-Wool showed bacteriostatic properties for all composites even after three months of being synthesised. This opens up potential applications for the use of MH and MGO in antimicrobial woollen apparel, medical textiles and bandages.</p> <p>In addition, MGO was incorporated into samples of an acrylic polymer NeoCryl® XK-98 and a polyurethane, Kamthane K-5000, polymer resin, respectively. The interaction of MGO with the respective polymer chains resulted in similar hydrogen bonding between MGO and the polymers. At high MGO concentrations this bonding was confirmed by the presence of a new endothermic peak in the DSC pattern. The addition of MGO also modified the polymer surface and resulted in a more hydrophobic surface with an increased water droplet contact angle of 87.5°. The new polymer compositeswere successfully tested against S. aureus and E. coli microbes and were shown to exhibit antimicrobial properties.</p>


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