Analysis Of Microbial Growth Research Articles

Heterotrophic plate counts (HPCs) in drinking water distribution systems: A comprehensive review and meta-analysis

ABSTRACT Heterotrophic plate count (HPC) is widely assessed in drinking water distribution systems. However, methodological standards and guidelines on the use of HPC are not clearly defined. This comprehensive review and meta-analysis aim to evaluate HPC concentration and how they relate to the characteristics and operational conditions of systems. The size of the distribution system, use of chlorine or chloramine as secondary disinfection and the carbon content of the water were considered. Among 839 MEDLINE® records, 39 met our criteria and were included in the meta-analysis. Overall, wide ranges of HPC levels were observed in drinking water distribution systems. Results from the meta-analysis show a significant difference in concentrations between systems using chlorine or chloramine as secondary disinfectant and those that are not using any form of secondary disinfection. Similarly, results demonstrate a positive correlation between HPC levels and assimilable organic carbon. Assessing the spatial and temporal variations of HPC can provide useful information about the biological stability of the water and allow for routine analyses within individual drinking water systems. Due to its limitations as a global and unique indicator of water quality, HPC should be applied as part of a multi-parameter approach for microbial growth analysis in distribution networks.

Automatically showing microbial growth kinetics with a high-performance microbial growth analyzer

It is difficult to show microbial growth kinetics online when they grow in complex matrices. We presented a novel strategy to address this challenge by developing a high-performance microbial growth analyzer (HPMGA), which employed a unique 32-channel capacitively coupled contactless conductivity detector as a sensing element and fixed with a CellStatz software. It was capable of online showing accurate and repeatable growth curves of well-dispersed and bad-dispersed microbes, whether they grew in homogeneous simple culture broth or heterogeneous complex matrices. Moreover, it could automatically report key growth kinetics parameters. In comparison to optical density (OD), plate counting and broth microdilution (BMD) methods, we demonstrated its practicability in five scenarios: 1) the illustration of the growth, growth rate, and acceleration curves of Escherichia coli (E. coli); 2) the antimicrobial susceptibility testing (AST) of Oxacillin against Staphylococcus aureus (S. aureus); 3) the determination of Ag nanoparticle toxicity on Providencia rettgeri (P. rettgeri); 4) the characterization of milk fermentation; and 5) the enumeration of viable pathogenic Vibrio in shrimp body. Results highlighted that the HPMGA method had the advantages of universality and effectivity. This technology would significantly facilitate the routine analysis of microbial growth in many fields (biology, medicine, clinic, life, food, environment, and ecology), paving an avenue for microbiologists to achieve research goals that have been inhibited for years due to a lack of practical analytical methods.

Evaluation of the Efficacy of Novel Self Disinfectant Solution in Irreversible Hydrocolloid Impression Material - An Experimental Study.

Irreversible hydrocolloid materials are widely used for both diagnostic and definitive impression procedures. Impressions can be disinfected by immersion or spraying in any compatible disinfectant. Disinfectants should not adversely affect the dimensional stability of the impression and physical properties of impression material and subsequent dental cast. The study aims to evaluate the efficacy of a hypochlorous disinfectant solution mixed with irreversible hydrocolloid on setting time, antibacterial efficacy, and dimensional stability. Three groups were made with one control group and three alginate impression was made for each participants in the maxillary arch with 24-hours intervals between one another using the same brand of commercially available chromatic alginate. The working and setting time were noted. Bacterial swabs were collected using a dry sterile cotton swab in the mid palatal region. Dental casts were made using type III gypsum. The working and setting time had significant differences whereas the dimension among the cast has no significant difference. Microbial growth analysis had distinct differences among the groups. The self disinfection method using a pioneer solution of hypochlorous HOCl (100 ppm) to mix the alginate impression material rather than the water with the same powder-liquid ratio prescribed by the manufacturer had the same dimensional stability with improved antimicrobial action.

Dynamical Analysis and Optimization of a Generalized Resource Allocation Model of Microbial Growth

Gaining a better comprehension of the growth of microorganisms is a major scientific challenge, which has often been approached from a resource allocation perspective. Simple mathematical self-replicator models based on resource allocation principles have been surprisingly effective in accounting for experimental observations of the growth of microorganisms. Previous work, using a three-variable resource allocation model, predicted an optimal resource allocation scheme for the adaptation of microbial cells to a sudden nutrient change in the environment. We here propose an extended version of this model considering also proteins responsible for basic housekeeping functions, and we study their impact on predicted optimal strategies for resource allocation following changes in the environment. A full dynamical analysis of the system shows there is a single globally attractive equilibrium, which can be related to steady-state growth conditions of bacteria observed in experiments. We then explore the optimal allocation strategies using optimization and optimal control theory. We show that the solutions to this dynamical problem have a complicated structure that includes a second-order singular arc given in feedback form, and characterized by i) Fuller's phenomenon, and ii) the turnpike effect, producing a very particular asymptotic behaviour towards the solution of the static optimization problem. Our work thus provides a generalized perspective on the analysis of microbial growth by means of simple self-replicator models.

Microbiological Analysis of Tilapia Fillet Stored Under Refrigerated Conditions

Fish is a food susceptible to deterioration and contamination by microorganisms through the food chain, affecting its quality and safety. Fish is subjected to various processing and preservation methods in order to maintain availability, quality and safety for a longer time. The objective of the study was the microbiological analysis of tilapia fillets in refrigeration for 12 days. The tilapia processing was carried out to obtain fillets. The fillets were packed in polyethylene bags and later in an isothermal polystyrene container and kept in refrigeration for 12 days and the microbiological analysis was carried out through quality and safety indicators. The results of the microbiological analysis indicated a regular growth dynamic during storage, reaching maximums for Aerobic Mesophylls (AM) and Aerobic Psychrophiles (AP) of 12.5 and 8.6 Log CFU/g respectively, Fungi and Yeast (FY) 9 Log CFU/g, Lactic Acid Bacteria (LAB) 9 Log CFU/g, Total Coliforms (TC) 8.3 Log CFU/g and Pseudomonas (P) 7 Log CFU/g. According to different microbiological criterion related to deterioration and acceptability in food, the counts obtained in fillet reached maximum values on day 4 of storage for AM, day 6 for AP, day 8 for P, day 2 for TC and after day 2 for LAB. The analysis of microbial growth in fillet under refrigeration through quality and safety indicators, allow estimating conditions and periods of availability of healthy and nutritious food.

AMiGA: Software for Automated Analysis of Microbial Growth Assays.

ABSTRACTThe analysis of microbial growth is one of the central methods in the field of microbiology. Microbial growth dynamics can be characterized by meaningful parameters, including carrying capacity, exponential growth rate, and growth lag. However, microbial assays with clinical isolates, fastidious organisms, or microbes under stress often produce atypical growth shapes that do not follow the classical microbial growth pattern. Here, we introduce the analysis of microbial growth assays (AMiGA) software, which streamlines the analysis of growth curves without any assumptions about their shapes. AMiGA can pool replicates of growth curves and infer summary statistics for biologically meaningful growth parameters. In addition, AMiGA can quantify death phases and characterize diauxic shifts. It can also statistically test for differential growth under distinct experimental conditions. Altogether, AMiGA streamlines the organization, analysis, and visualization of microbial growth assays.IMPORTANCE Our current understanding of microbial physiology relies on the simple method of measuring microbial populations’ sizes over time and under different conditions. Many advances have increased the throughput of those assays and enabled the study of nonlab-adapted microbes under diverse conditions that widely affect their growth dynamics. Our software provides an all-in-one tool for estimating the growth parameters of microbial cultures and testing for differential growth in a high-throughput and user-friendly fashion without any underlying assumptions about how microbes respond to their growth conditions.

Microbial characterization of the Japanese traditional pickle senmaizuke produced by two different manufacturing processes.

Senmaizuke, a traditional turnip pickle, prepared in Kyoto, Japan, is produced via two types of manufacturing processes: with and without vinegar for fermentation. The aim of this study was to reveal the microbial community and growth behavior in the products and manufacturing processes of two types of senmaizuke. Microbial growth analysis of commercial senmaizuke products showed that both types harbored 102–108 colony forming units (CFU)/g of lactic acid bacteria (LAB) and 102–104 of yeast. The fermented‐type products showed successive growth of LAB during the pickling and ripening processes, whereas LAB in vinegar‐type products showed growth only at the preliminary pickling step before vinegar addition; however, the bacteria were viable at the ripening step. LAB in the vinegar‐type products showed growth when the pH of the pickle was neutralized, indicating that acidification via vinegar retards LAB growth. Metagenomic sequencing showed that the fermented‐type products harbored Lactobacillus, Leuconostoc, and other halophilic and psychrophilic bacteria, with a higher bacterial diversity than in the vinegar‐type products. In the vinegar‐type products, Lactobacillus, Leuconostoc, or both were predominant. Culture tests using LAB isolates and turnip medium suggested that a change in the dominance of Leuconostoc to Lactobacillus members observed in the fermented‐type products during pickling and ripening processes was attributed to the low pH sensitivity of Leuconostoc as well as a relatively long lag phase of growth for adapting to the pickling environment. The findings of this study will be useful for the appropriate quality control and assurance procedure of senmaizuke.

Antibacterial Activity of Silver Nanoparticles (AgNP) Confined to Mesostructured, Silica-Based Calcium Phosphate Against Methicillin-Resistant Staphylococcus Aureus (MRSA).

Staphylococcus aureus, which is commonly found in hospitals, has become a major problem in infection control. In this study, Ag/80S bioactive ceramics used for enhanced antibacterial applications have been developed. An in vitro bioactivity test of the Ag/80S bioactive ceramic powders was performed in a phosphate-buffered saline (PBS). To explore the antibacterial activity of the Ag/80S bioactive ceramic powders, the Kirby-Bauer susceptibility test, the kinetics of microbial growth analysis and the colony-forming capacity assay were used to determine their minimum inhibitory concentration (MIC) against methicillin-resistant Staphylococcus aureus (MRSA). The results confirmed that the Ag/80S bioactive ceramic powders have antibacterial activity against MRSA (ATCC 33592) and MRSA (ATCC 49476).

Vibrio parahaemolyticus ATCC 17802 inactivation by using methylcellulose films containing encapsulated bacteriophages

In the present study, it was aimed to inactivate Vibrio parahaemolyticus ATCC 17802, which is an important human pathogen, by making use of edible methylcellulose films containing encapsulated bacteriophages. For this purpose, the bacteriophages used as biocontrol agents specific for V. parahaemolyticus ATCC 17802 were isolated from raw bonito fishes (Sarda sarda) and then purified, and finally the stabilities of isolated bacteriophages were determined. The pure bacteriophage filtrates were encapsulated with sodium alginate by employing an extrusion method and the edible methylcellulose films were prepared. The bacteriophage stabilities of the prepared films were analyzed on the 0th, 4th, 7th, and 14th days of storage in a refrigerator (4 °C) under darkness and in illuminated room (22 °C) conditions. The methylcellulose films were determined to release bacteriophages to the environment and into raw fish fillets and antimicrobial effects of these films were detected against V. parahaemolyticus. In conclusion, a specific antimicrobial effect on V. parahaemolyticus ATCC 17802 was achieved by using edible methylcellulose films containing encapsulated bacteriophages. The results of microbial growth analysis showed an approximately 2.65 log difference in microbial levels between the control and the treatment samples. By maintaining the bacteriophage stability of prepared films, a new film that reinforces bacteriophage release was developed.

Implications of uncertain bioreactive parameters on a complex reaction network of atrazine biodegradation in soil

Abstract We study propagation of uncertainty related to bioreactive parameters through the biodegradation reaction network of atrazine (ATZ) and its metabolites in soils. The work is motivated by the recognition that detailed analyses of these aspects in models of complex biogeochemical systems is especially critical when the feedback amongst hydraulic, chemical and microbial processes is strong. With an emphasis on microbial processes, the ATZ reaction network is exemplary because it includes 19 biological reactions mediated by 3 microbial functional groups that compete in 6 metabolic and co-metabolic degradation pathways under aerobic and anaerobic conditions. Propagation of model parametric uncertainty yields the probability distributions of ATZ, its metabolites, and the microbial biomass. It also enables us to identify key parameters that drive the long-term system dynamics. We base our analyses on an initial screening of model parameters and a subsequent moment-based global sensitivity analysis, and we show that the probability density of target outputs are multimodal as a result of nonlinearities in the degradation rate formulations. The employed global sensitivity metrics reveal that joint effects of the uncertainty of multiple kinetic parameters significantly contribute to output uncertainties, thus suggesting the presence of a high level of coupling between processes included in the network. Specific biomass affinity to a given substrate is found to be a lumped indicator that can facilitate the analysis of microbial growth when multiple and competing microbial functional groups coexist.

Automated rapid blood culture sensor system based on diode laser wavelength-modulation spectroscopy for microbial growth analysis

An automated rapid blood culture sensor system was developed to detect CO2 concentration levels in blood culture bottles and thereby monitoring microbial growth. The sensor system is based on diode laser wavelength-modulation spectroscopy (DLWMS), which offers low cost, high sensitivity, fast response as well as label-free and non-intrusive detection. The optical gas sensing module was based on a careful design to realize automated and rapid CO2 detection with the assistance of control and storage elements. A 2-month field test was carried out at the Jinhua Guangfu Hospital, Jinhua, China for the new DLWMS based sensor system, which exhibits similar performance to a commercial BacT/ALERT 3D automated blood culture system in terms of accuracy but with significantly reduced detection time.

Real-time analysis of microbial growth by means of the Heat-Transfer Method (HTM) using Saccharomyces cerevisiae as model organism

In this manuscript, we explore the use of the Heat-Transfer Method (HTM) for the real-time analysis of microbial growth using Saccharomyces cerevisiae as a model organism. The thermal responses of gold electrodes upon exposure to suspensions of S. cerevisiae (wild type strain DLY640) concentrations were monitored, demonstrating an increase in thermal resistance at the solid-liquid interface with higher concentrations of the microorganism. Flow cells were manufactured using 3D-printing to facilitate longitudinal experiments.We can clearly discriminate between the growth of S. cerevisiae under optimal conditions and under the influence of factors that inhibit the replication process, such as the use of nutrient depleted growth medium, elevated temperature, and the presence of toxic compounds. In addition, it is possible to determine the kinetics of the growth process and quantify yeast replication which was demonstrated by measuring a mutant temperature sensitive strain.This is the first time HTM has been used for the real-time determination of factors that impact microbial growth. Thermal sensing is low-cost, offers straightforward analysis and measurements can be performed on-site. Due to the versatility of this method, this platform can be extended to monitor other microorganisms and in particular to study the response of bacteria to selected antibiotics.

Nature of Insoluble Material Found in the Bottom of Soybean Biodiesel Storage Tank: Chemical and Microbiological Approach

During biodiesel storage, chemical reactions may occur, producing sludges. The aim of this study was to characterize the chemical and microbial composition of the sludge found in a biodiesel storage tank. The material was collected in a biodiesel production plant. The sludge chemical characterization was performed by Fourier transform infrared (FTIR) spectroscopy, flame atomic absorption spectroscopy (FAAS), gas chromatography (GC), and the microbial investigation used culture-dependent techniques. The deteriogenic potential of the native microbial community was evaluated using the sludge as a microbial inoculum in a 60 day experiment. The microbial growth, biodiesel degradation, pH alterations, and the detection of esters in the aqueous phase were evaluated. The chemical analysis indicated the sludge composition as fatty acids esters and metallic ions; sterols glycosides were not detected. Seven bacteria and five fungi species were obtained from the sludge. The microbial growth analysis indicated that the native community does not have high biodiesel deteriogenic capacity.

Isolation and characterization of PAH-degrading bacteria from the Eastern Province, Saudi Arabia

Contaminated sediment samples were collected from the Eastern Province, Saudi Arabia for isolation of pyrene- and phenanthrene-degrading bacteria by enrichment method. Four isolates were morphologically characterized as Gram-negative rod strains and 16S rRNA sequence analysis revealed the isolates as closely related to Pseudomonas aeruginosa, P. citronellolis, Ochrobactrum intermedium and Cupriavidus taiwanensis. Degradation of the polycyclic aromatic hydrocarbons (PAHs) by the latter three strains was investigated in liquid cultures. Results of concentration reduction analyzed with gas chromatography show that P. citronellolis_LB was efficient in removing phenanthrene, degrading 94% of 100ppm in 15days while O. intermedium_BC1 was more efficient in pyrene-removal, degrading 62% in 2weeks. Furthermore, bacterial growth assessment using optical density and population counts revealed the latter as more suitable for microbial growth analysis in PAH-containing cultures. In conclusion, the isolated bacterial strains could be further developed for efficient use in biodegradation of PAH.

Spotsizer: High-throughput quantitative analysis of microbial growth.

Microbial colony growth can serve as a useful readout in assays for studying complex genetic interactions or the effects of chemical compounds. Although computational tools for acquiring quantitative measurements of microbial colonies have been developed, their utility can be compromised by inflexible input image requirements, non-trivial installation procedures, or complicated operation. Here, we present the Spotsizer software tool for automated colony size measurements in images of robotically arrayed microbial colonies. Spotsizer features a convenient graphical user interface (GUI), has both single-image and batch-processing capabilities, and works with multiple input image formats and different colony grid types. We demonstrate how Spotsizer can be used for high-throughput quantitative analysis of fission yeast growth. The user-friendly Spotsizer tool provides rapid, accurate, and robust quantitative analyses of microbial growth in a high-throughput format. Spotsizer is freely available at https://data.csiro.au/dap/landingpage?pid=csiro:15330 under a proprietary CSIRO license.

Quantifying the sensitivity of G. oxydans ATCC621H and DSM 3504 to osmotic stress triggered by soluble buffers.

In Gluconobacter oxydans cultivations on glucose, CaCO3 is typically used as pH-buffer. This buffer, however, has disadvantages: suspended CaCO3 particles make the medium turbid, thereby, obstructing analysis of microbial growth via optical density and scattered light. Upon searching for alternative soluble pH-buffers, bacterial growth and productivity was inhibited most probably due to osmotic stress. Thus, this study investigates in detail the osmotic sensitivity of G. oxydans ATCC621H and DSM3504 using the Respiratory Activity MOnitoring System. The tested soluble pH-buffers and other salts attained osmolalities of 0.32-1.19osmolkg(-1). This study shows that G. oxydans ATCC 621H and DSM 3504 respond quite sensitively to increased osmolality in comparison to other microbial strains of industrial interest. Osmolality values of >0.5osmolkg(-1) should not be exceeded to avoid inhibition of growth and product formation. This osmolality threshold needs to be considered when working with soluble pH-buffers.

Material Characterization and Biodegradation Assessment of Mural Paintings: Renaissance Frescoes from Santo Aleixo Church, Southern Portugal

The aim of this work is the material characterization of wall paintings and biodegradation assessment, including the analysis of microbial growth and the effect of microbial proliferation, in view of their conservation. The methodology was applied to the study of frescoes dated from 1531, located in the ancient parish church of Santo Aleixo, Southern Portugal. The combined use of optical microscopy, scanning electron microscopy coupled with energy dispersive X-ray spectrometry (SEM-EDS) and μ- X-ray diffraction (XRD) showed that the painting palette is composed of red and yellow ochers, malachite, azurite, and bone black. The pigments do not show signs of chemical deterioration, except for malachite, which transformed to black copper oxide (tenorite). The microbiological study allowed the identification of several bacterial strains (e.g., Gram+ cocci, Gram+ bacilli, Actinomycetes sp.), yeast strains, and filamentous fungi of the genera Penicillium, Cladosporium and Aspergillus, among others of the microflora present in the paintings. Their metabolic activity is primarily responsible for the physical disruption of paint layers and underlying mortars. The combined approach using SEM analysis and enzymatic dehydrogenase measurement allowed the evaluation of microflora proliferation and diagnosis of the biodeterioration of the mural paintings. Additionally, the effect of some commercial biocides was evaluated for the predominant strains in order to select the most efficient biocide.

Encapsulation of bacteriophages in whey protein films for extended storage and release

The overall motivation of this study was to enable development of pathogen specific antimicrobial packaging materials. These materials are expected to have a significant impact in improving efficacy of antimicrobial treatment and retention of commensal and probiotic microbes on food materials. To achieve these goals, this study was aimed at encapsulation of a model bacteriophage, T4 bacteriophage, in WPI based edible protein films. Phage encapsulated WPI films were characterized for stability and release of encapsulated phages. Antimicrobial efficacy of phage encapsulating edible films was characterized using a microbial growth inhibition assay. Distribution of phages in edible film was measured using a confocal fluorescence microscopy. The results demonstrate that the WPI films are able to stabilize phages at ambient (22 °c and light) and refrigerated (4 °C and dark) conditions without significant loss in phage infectivity over a period of one month. Additionally, the WPI films are able to release a significant concentration of phages in an aqueous environment and leaf surface within 3 h of incubation. Antimicrobial activity measurements demonstrate that the phage encapsulating WPI film can effectively inhibit the microbial growth. The results of microbial growth analysis showed an approximately 5 log difference in microbial levels between the control and the treatment samples. Confocal imaging measurements show that fluorescently labeled phages are homogenously distributed within the WPI film matrix. Overall, this study demonstrates integration of phages with edible packaging materials to develop novel active packaging materials for biocontrol applications.

HSP70 Overexpression in Response to Ureaplasma urealyticum–Mediated Oxidative Stress In Preeclamptic Placenta

Objective. To determine the effect of Ureaplasma urealyticum infection on oxidative stress during preeclampsia. Methods. The relationship between oxidative stress and U. urealyticum infection was monitored through the estimation of lipid hydroperoxidation level (LHP), glutathione redox ratio (GRR), and total antioxidant capacity (TAC) along with heat shock protein 70 (HSP70) expression in the placenta. Microbial growth analysis was used for U. urealyticum detection. Results. U. urealyticum infection was found in 43.7% of the preeclamptic subjects. The increased LHP level (p < 0.05) along with decreased GRR (p < 0.05) and TAC (p < 0.05) was noted in preeclamptic patients with U. urealyticum infection compared with uninfected preeclamptic and normal subjects. Under such condition, an increase in the HSP70 levels in the infected preeclamptic samples by 24.6% (p < 0.05) on comparison with uninfected preeclamptic samples was observed. Conclusion. Overexpression of HSP70 in the placental homogenate suggests the contribution of infection to oxidative stress development and the possible protective role of HSP70 against infection.

Effects of initial low oxygen and perforated film package on quality of fresh‐cut cabbages

AbstractThe effects of perforated film packages (PFP) with different oxygen partial pressures (5, 8 and 10 kPa) and a barrier package (BP) at 21 kPa of O2 on the quality of fresh‐cut cabbages were studied at 5 and 20 °C. The microbial growth, appearance, flavor, ascorbic acid content and polyphenol oxidase activity were determined during storage. The results indicated that fresh‐cut cabbages had better color retention and quality in PFP. Oxidation of ascorbic acid (AA) and browning of fresh‐cut cabbage were inhibited effectively using a PFP and an initial oxygen partial pressure equal to 5 kPa. Analysis of microbial growth also showed that the total count on fresh‐cut cabbage was relative lower in PFP with an initial low O2 content. Loss of total ascorbic acid was much lower in PFP than that in BP by suppressing AA oxidation. The results of sensory evaluation showed that flavor and appearance were maintained effectively at 5 °C and significant differences in flavor were found between PFP and BP both at 5 and 20 °C, while significant differences in appearance were found between PFP and BP only at 20 °C. Copyright © 2007 Society of Chemical Industry