Bacterial Growth Conditions Research Articles

ANALISIS PRODUK DARAH: KONTAMINASI BAKTERI PADA THROMBOCYTE CONCENTRATE

Background: Bacterial contamination in thrombocyte concentrate (TC) blood product becomes a serious problem since it can cause clinical risks from mild symptom to death. TC storage condition at 22-25oC with agitation is good condition for bacterial growth. Source of bacterial contamination can come from donor bacteremia, not aseptically from taking and processing blood product. In a previous study, showed there were positive gram bacteria as bacterial contamination in TC.
 Objective: This objective aims to determine bacterial contaminants in TC blood products. 
 Methods: Total of 3 TC bag samples were collected from UDD PMI Kabupaten Sleman. Each sample was inoculated to nutrient agar media and it incubated for 48 jam at 37oC. Observation of bacterial colony growth is carried out after incubation time is over.
 Results: There was no bacterial growth in the media so that there was no bacterial contamination in TC. It showed that the procedures, processing, and storage of TC products in PMI Kabupaten Sleman were aseptic. Besides that, TC donors also did not suffer from bacteremia so there was bacterial contamination in TC.
 Conclusion: In this study, bacterial contamination in blood product TC was not found since there was no bacterial growth in media. 
 Keywords: Bacterial contamination, blood products, blood bank, thrombocyte concentrate.

ODX: A Fitness Tracker-Based Device for Continuous Bacterial Growth Monitoring.

Continuous monitoring of bacterial growth in aqueous media is a crucial process in academic research as well as in the biotechnology industry. Bacterial growth is usually monitored by measuring the optical density of bacteria in liquid media, using benchtop spectrophotometers. Due to the large form factor of the existing spectrophotometers, they cannot be used for live monitoring of the bacteria inside bacterial incubation chambers. Additionally, the use of benchtop spectrometers for continuous monitoring requires multiple samplings and is labor intensive. To overcome these challenges, we have developed an optical density measuring device (ODX) by modifying a generic fitness tracker. The resulting ODX device is an ultraportable and low-cost device that can be used inside bacterial incubators for real-time monitoring even while shaking is in progress. We evaluated the performance of ODX with different bacterial types and growth conditions and compared it with a commercial benchtop spectrophotometer. In all cases, ODX showed comparable performance to that of the standard benchtop spectrophotometer. Finally, we demonstrate a simple and useful smartphone application whereby the user is notified when the bacterial concentration reaches the targeted value. Due to its potential for automation and mass production, we believe that the ODX has a wide range of applications in biotechnology research and industry.

Selection of bacteria inducing calcium carbonate precipitation for self-healing concrete application

A modification of bacterial medium using calcium lactate pentahydrate was developed for calcium carbonate precipitation. A total of five strains of bacteria were cultivated on the solution medium containing nutrient broth and calcium lactate pentahydrate. In this study, the variation of 3.2 mM and 16.2 mM of calcium lactate pentahydrate was used to obtain the optimum condition for bacterial growth. The results showed that isolated strains CPB 1, CPB 3, and CPB 5 with medium containing nutrient broth and 3.2 mM calcium lactate pentahydrate gave the optimum growth, pH and Eh, thus being favourable for the process of calcium carbonate precipitation. Hence, this will be useful for self-healing concrete.

Combining Modules for Versatile and Optimal Labeling of Lactic Acid Bacteria: Two pMV158-Family Promiscuous Replicons, a Pneumococcal System for Constitutive or Inducible Gene Expression, and Two Fluorescent Proteins.

Labeling of bacterial cells with fluorescent proteins allows tracking the bacteria in competition and interactomic in vivo and in vitro studies. During the last years, a few plasmid vectors have been developed aimed at the fluorescent labeling of specific members of the lactic acid bacteria (LAB), a heterogeneous group that includes microorganisms used in the food industry, as probiotics, or as live vectors for mucosal vaccines. Successful and versatile labeling of a broad range of LAB not only requires a vector containing a promiscuous replicon and a widely recognized expression system for the constitutive or regulated expression of the fluorescence determinant, but also the knowledge of the main features of the entire plasmid/host/fluorescent protein ensemble. By using the LAB model species Lactococcus lactis, we have compared the utility properties of a set of labeling vectors constructed by combining a promiscuous replicon (pMV158 or pSH71) of the pMV158 plasmid family with the gene encoding either the EGFP or the mCherry fluorescent protein placed under control of promoter PX or PM from the pneumococcal mal gene cluster for maltosaccharide uptake and utilization, respectively. Some vectors carrying PM also harbor the malR gene, whose product represses transcription from this promoter, thus enabling maltose-inducible synthesis of the fluorescent proteins. We have determined the plasmid copy number (PCN) and segregational stability of the different constructs, as well as the effect of these features on the fitness and fluorescence intensity of the lactococcal host. Constructs based on the pSH71 replicon had a high copy number (∼115) and were segregationally stable. The copy number of vectors based on the pMV158 replicon was lower (∼8–45) and varied substantially depending on the genetic context of the plasmid and on the bacterial growth conditions; as a consequence, inheritance of these vectors was less stable. Synthesis of the fluorescent proteins encoded by these plasmids did not significantly decrease the host fitness. By employing inducible expression vectors, the fluorescent proteins were shown to be very stable in this bacterium. Importantly, conditions for accurate quantification of the emitted fluorescence were established based on the maturation times of the fluorescent proteins.

Adaptation of acneic and non acneic strains of Cutibacterium acnes to sebum-like environment.

Cutibacterium acnes, former Proprionibacterium acnes, is a heterogeneous species including acneic bacteria such as the RT4 strain, and commensal bacteria such as the RT6 strain. These strains have been characterized by metagenomic analysis but their physiology was not investigated until now. Bacteria were grown in different media, brain heart infusion medium (BHI), reinforced clostridial medium (RCM), and in sebum like medium (SLM) specifically designed to reproduce the lipid rich environment of the sebaceous gland. Whereas the RT4 acneic strain showed maximal growth in SLM and lower growth in RCM and BHI, the RT6 non acneic strain was growing preferentially in RCM and marginally in SLM. These differences were correlated with the lipophilic surface of the RT4 strain and to the more polar surface of the RT6 strain. Both strains also showed marked differences in biofilm formation activity which was maximal for the RT4 strain in BHI and for the RT6 strain in SLM. However, cytotoxicity of both strains on HaCaT keratinocytes remained identical and limited. The RT4 acneic strain showed higher inflammatory potential than the RT6 non acneic strain, but the growth medium was without significant influence. Both bacteria were also capable to stimulate β‐defensine 2 secretion by keratinocytes but no influence of the bacterial growth conditions was observed. Comparative proteomics analysis was performed by nano LC‐MS/MS and revealed that whereas the RT4 strain only expressed triacylglycerol lipase, the principal C. acnes virulence factor, when it was grown in SLM, the RT6 strain expressed another virulence factor, the CAMP factor, exclusively when it was grown in BHI and RCM. This study demonstrates the key influence of growth conditions on virulence expression by C. acnesand suggest that acneic and non acneic strains are related to different environmental niches.

Bacterial fitness in chronic wounds appears to be mediated by the capacity for high-density growth, not virulence or biofilm functions.

While much is known about acute infection pathogenesis, the understanding of chronic infections has lagged. Here we sought to identify the genes and functions that mediate fitness of the pathogen Pseudomonas aeruginosa in chronic wound infections, and to better understand the selective environment in wounds. We found that clinical isolates from chronic human wounds were frequently defective in virulence functions and biofilm formation, and that many virulence and biofilm formation genes were not required for bacterial fitness in experimental mouse wounds. In contrast, genes involved in anaerobic growth, some metabolic and energy pathways, and membrane integrity were critical. Consistent with these findings, the fitness characteristics of some wound impaired-mutants could be represented by anaerobic, oxidative, and membrane-stress conditions ex vivo, and more comprehensively by high-density bacterial growth conditions, in the absence of a host. These data shed light on the bacterial functions needed in chronic wound infections, the nature of stresses applied to bacteria at chronic infection sites, and suggest therapeutic targets that might compromise wound infection pathogenesis.

Low Endotoxin Recovery-Masking of Naturally Occurring Endotoxin.

Endotoxins are cell wall components of Gram-negative bacteria. A release of endotoxins into the human blood stream results in an inflammation reaction that can lead to life-threatening conditions like sepsis. Therefore, control for endotoxin contamination of intravenously administered drugs is crucial. Drugs are usually tested for putative endotoxin contamination with Limulus-based tests. However, validity of the compendial test procedures is questioned in the case of low endotoxin recovery (LER). To assure validity, regulatory authorities request hold-time studies of endotoxin in addition to pharmacopoeial requirements. Within these studies, endotoxin is added (spiked) to an undiluted product. The spiked product is held for a certain period of time and subsequently diluted for endotoxin determination. Due to the known heterogeneity of endotoxin the question has been raised as to which source represents the most adequate endotoxin spike. In the present study, endotoxin hold-time studies were analyzed by using different sources of endotoxin. Highly purified endotoxin, crude endotoxin extracts (Naturally Occurring Endotoxin) from different bacterial species and varied growth conditions as well as endogenous endotoxin contaminations were investigated. The results clearly demonstrate that endotoxin masking—an effect of LER—is dependent on the endotoxin source used. Various parameters such as bacterial strain and growth conditions lead to different masking susceptibilities. Due to these effects it is impossible to predict the susceptibility of bacterial endotoxin contamination to LER. In order to determine whether a sample is prone to LER, an endotoxin spike that is susceptible to LER is required.

Evaluating iron as a biomarker of rhythmites — An example from the last Paleozoic ice age of Gondwana

Microorganisms play a significant role in mineral precipitation, but detecting them in the fossil record is still a challenge. Here we offer an example of how the detection of biological activity in the sedimentary environment can modify a classical depositional model. This study describes the activity of microorganisms in sedimentary structures and the iron mineral formation during the last Paleozoic Ice Age in southwestern Gondwana, recorded by the “Itu rhythmites”, Paraná Basin, Brazil. The Itu rhythmites have been considered to be varve-type deposits that present alternating dark laminae (clay/silt-size sediments) and light layers (sand/gravel-size sediments) of varied thickness, forming couplets. Earlier studies focused on abiotic processes of these structures. We applied different techniques and analytical approaches were used, such as synchrotron-based techniques and rock magnetic techniques, in order to test the biogenicity of iron minerals contained in putative microbially-induced sedimentary structures. By detecting biominerals in this rock succession, the depositional model had to be reconsidered, taking into account the biological activity, the limitations on the specific conditions for bacterial growth, and for mineral precipitation. Therefore, we offer a new depositional model that considers the role of microorganisms in formation of these laminae, and this model can be considered for other iron-rich rhythmic deposits in other places of the world. Considering the effects of temperature and other factors in the bacterial productivity, the deposition of the latest couplets in the outcrop occurred in different seasons and by different depositional processes, corroborating with the non-periodicity of 1 year per lithological couplet.

ANALISIS PRODUK DARAH: KONTAMINASI BAKTERI PADA THROMBOCYTE CONCENTRATE

Background: Bacterial contamination in thrombocyte concentrate (TC) blood product becomes a serious problem since it can cause clinical risks from mild symptom to death. TC storage condition at 22-25oC with agitation is good condition for bacterial growth. Source of bacterial contamination can come from donor bacteremia, not aseptically from taking and processing blood product. In a previous study, showed there were positive gram bacteria as bacterial contamination in TC.
 Objective: This objective aims to determine bacterial contaminants in TC blood products. 
 Methods: Total of 3 TC bag samples were collected from UDD PMI Kabupaten Sleman. Each sample was inoculated to nutrient agar media and it incubated for 48 jam at 37oC. Observation of bacterial colony growth is carried out after incubation time is over.
 Results: There was no bacterial growth in the media so that there was no bacterial contamination in TC. It showed that the procedures, processing, and storage of TC products in PMI Kabupaten Sleman were aseptic. Besides that, TC donors also did not suffer from bacteremia so there was bacterial contamination in TC.
 Conclusion: In this study, bacterial contamination in blood product TC was not found since there was no bacterial growth in media. 
 Keywords: Bacterial contamination, blood products, blood bank, thrombocyte concentrate.

Production of antioxidant exopolysaccharide from Pseudomonas aeruginosa utilizing heavy oil as a solo carbon source

Aim/Background: Pseudomonas aeruginosa is capable of utilizing heavy oil hydrocarbons as a sole carbon source. P. aeruginosa produce exopolysaccharide (EPS) in an inorganic medium in the presence of crude oil. Several environmental factors affect the majority of EPS production. Materials and Methods: Strain of P. aeruginosa were managed under various media (maintenance medium, inoculum, and basal media). Different heavy petroleum oil concentrations (5, 10, 20, and 30 ml/L) were used as solo carbon source to the basal medium. Various conditions of bacterial growth were monitored. The growth of cells was estimated by measuring the absorbance of the mixture of 1 ml of the basal medium diluted with 1 ml of distilled water at 600 nm spectrophotometrically. P. aeruginosa was grown aerobically in a production medium at 37°C and 150 rpm on a rotary shaker. The culture broth was centrifuged to separate the cells. The precipitated polysaccharide was separated by centrifugation and washed with ethanol, acetone, and ether, and then dried under reduced pressure oven at 45°C. The DPPH test was carried out as described by Burits and Bucar to monitor the free radical scavenging activities of the extracts. Results: The preferable culture conditions for EPS production were at 10 ml/L heavy oil, with 0.5 g/L NaNO3as best N sources at pH 6.0 after 5 days incubation. The net weight of purified EPS production was 0.5 g/L. Conclusion: The obtained polysaccharide showed antioxidant activity that possesses DPPH radical scavenging activity, with an EC50 =0.201.

Optimization Conditions for Maximum Oil Bioremediation and Biopolymer Production by Pseudomonads

The main objective of the present study was to isolate polyhydroxyalkanoate-producing pseudomonads from the petroleum hydrocarbon-contaminated area, investigate bioremediation potential of these bacteria and then optimize the culture conditions for maximum bacterial growth and polyhydroxyalkanoate production from crude oil. Forty-five oil-degrading pseudomonads were isolated and 15 polyhydroxyalkanoate-producing pseudomonads have been detected. Temperature = 30 °C, incubation time = 7 days, polyhydroxyalkanoates production media and 2% (V/V) crude oil were selected as the optimum conditions for maximum bacterial growth and polyhydroxyalkanoates accumulation. Finally, the produced biopolymers were characterized by gas chromatography/mass spectrometry. Under the optimal conditions, the highest bacterial growth (optical density 600 nm) and polyhydroxyalkanoates content (% W/W) were 0.35 ± 0.05 and 22.25 ± 0.13, respectively. The present study shows that unfavorable conditions such as petroleum-contaminated area can be potential resources for polyhydroxyalkanoates producers. These isolates could be used in future bioremediation of hydrocarbons while producing industrially relevant polymers as a by-product at the optimal condition.

The Characteristics and Dynamics of Cyanobacteria-Heterotrophic Bacteria Between Two Estuarine Reservoirs - Tropical Versus Sub-Tropical Regions.

In this study, Illumina MiSeq sequencing technique was employed to explore the characteristics and dynamics of cyanobacteria–heterotrophic bacteria between two estuarine reservoirs in sub-tropical (reservoir A in Shanghai) and tropical (reservoir B in Singapore) regions. The results indicated that significant differences in bacterial community composition were found between two estuarine reservoirs, which influenced by varied environmental variables. The environmental heterogeneity in reservoir A was much higher, which indicated that the composition of bacterial community in reservoir A was more complex. In contrast, reservoir B provided a suitable and temperate water environment conditions for bacterial growth, which resulted in higher community diversity and less co-exclusion correlations. The molecular ecological network indicated that the presence of dominant bacterial community in each of the reservoir were significant different. These differences mainly reflected the responses of bacterial community to the variations of environmental variables. Although Synechococcus was the dominant cyanobacterial species in both reservoirs, it exhibited co-occurrence patterns with different heterotrophic bacteria between reservoirs. In addition, the cyanobacteria–heterotrophic bacteria interaction exhibited highly dynamic variations, which was affected by nutrition and survive space. Also, the co-occurrence of Microcystis and Pseudanabaena found in reservoir B implied that the non-N-fixing Microcystis accompanied with N-fixing Pseudanabeana occurrence in freshwater lakes, so as to better meet the demand for nitrogen source.

Predicting bacterial growth conditions from mRNA and protein abundances.

Cells respond to changing nutrient availability and external stresses by altering the expression of individual genes. Condition-specific gene expression patterns may thus provide a promising and low-cost route to quantifying the presence of various small molecules, toxins, or species-interactions in natural environments. However, whether gene expression signatures alone can predict individual environmental growth conditions remains an open question. Here, we used machine learning to predict 16 closely-related growth conditions using 155 datasets of E. coli transcript and protein abundances. We show that models are able to discriminate between different environmental features with a relatively high degree of accuracy. We observed a small but significant increase in model accuracy by combining transcriptome and proteome-level data, and we show that measurements from stationary phase cells typically provide less useful information for discriminating between conditions as compared to exponentially growing populations. Nevertheless, with sufficient training data, gene expression measurements from a single species are capable of distinguishing between environmental conditions that are separated by a single environmental variable.

Biodegradable plastic production by Bacillus spp. isolated from agricultural wastes and genetic analysis of PHA synthesis

Abstract Polyhydroxyalkanoates (PHAs) are resources that hoard by a variety of microorganisms as nutrient source. It is environmentally recyclable biopolymer, and totally corrupted biologically to simple molecules. A total of 38 isolates from agricultural wastes, 9 isolates exhibited optimistic outcome (dark blue particles) for PHA accumulation when stain by Sudan black B. Maximum bacterial growth was achieved at temperature 35°C, PH 7, (48-72) hr incubation and 0.25% concentration of NaCl. Chosen isolate (NE1MOK) recognized as Bacillus subtilis when diagnosed by traditional and molecular methods by amplification 16s rRNA gene. Bacillus subitilis had ability to accumulate 0.26 g/l (40.625 %) of PHA, and characterized by Fourier transforms infrared (FTIR) analysis which exhibited functional groups of PHA as (C-O, C=O, CH2, CH3, C-O-C, C-H and terminal OH). PCR results for amplification of synthase genes showed positive results in all isolates and length of amplicons was 505 bp. The aim of this study was to use agricultural wastes as a source to select bacterial isolates which produce PHAs, and determined the optimal conditions of bacterial growth, then analyze the genes responsible of its formation.

An optimum condition of MICP indigenous bacteria with contaminated wastes of heavy metal

Heavy metals are naturally occurring trace elements present in the environment, including soil, water, and air. However, high heavy metal concentration contamination from waste is a serious environmental problem brought on by industrial activities. The research in this study evaluated different biomineralized CaCO3 forms from individual bacteria species in heavy-metal-contaminated soils and mine tailings. Scanning electron microscope (SEM) images of the crystals were used to characterize the precipitated CaCO3. Generally, urea-hydrolysis bacteria form minerals via a microbiologically induced calcite precipitation (MICP) process. These bacteria produce the urease enzyme, which leads to urea-hydrolysis. These bacteria were isolated from heavy-metal-contaminated soils and characterized for their potential utilization in the S/S process. Optimum conditions for indigenous bacterial growth were 30 °C and a pH range of 7–8; and growth patterns were further affected by the growth medium salinity. SEM and X-ray diffraction (XRD) analyses demonstrated that bioaccumulated heavy metal ions were deposited around the cell envelope as rhombohedral and sphere shaped crystalline carbonate minerals in optimum conditions. In this study, the authors hypothesize that the indigenous bacteria can effectively precipitate heavy metals in soil and mine tailing with the urea-hydrolysis enzyme, and play an important role in heavy metal stabilization.

Fine grained compositional analysis of Port Everglades Inlet microbiome using high throughput DNA sequencing.

BackgroundSimilar to natural rivers, manmade inlets connect inland runoff to the ocean. Port Everglades Inlet (PEI) is a busy cargo and cruise ship port in South Florida, which can act as a source of pollution to surrounding beaches and offshore coral reefs. Understanding the composition and fluctuations of bacterioplankton communities (“microbiomes”) in major port inlets is important due to potential impacts on surrounding environments. We hypothesize seasonal microbial fluctuations, which were profiled by high throughput 16S rRNA amplicon sequencing and analysis.Methods & ResultsSurface water samples were collected every week for one year. A total of four samples per month, two from each sampling location, were used for statistical analysis creating a high sampling frequency and finer sampling scale than previous inlet microbiome studies. We observed significant differences in community alpha diversity between months and seasons. Analysis of composition of microbiomes (ANCOM) tests were run in QIIME 2 at genus level taxonomic classification to determine which genera were differentially abundant between seasons and months. Beta diversity results yielded significant differences in PEI community composition in regard to month, season, water temperature, and salinity. Analysis of potentially pathogenic genera showed presence of Staphylococcus and Streptococcus. However, statistical analysis indicated that these organisms were not present in significantly high abundances throughout the year or between seasons.DiscussionSignificant differences in alpha diversity were observed when comparing microbial communities with respect to time. This observation stems from the high community evenness and low community richness in August. This indicates that only a few organisms dominated the community during this month. August had lower than average rainfall levels for a wet season, which may have contributed to less runoff, and fewer bacterial groups introduced into the port surface waters. Bacterioplankton beta diversity differed significantly by month, season, water temperature, and salinity. The 2013–2014 dry season (October–April), was warmer and wetter than historical averages. This may have driven significant differences in beta diversity. Increased nitrogen and phosphorous concentrations were observed in these dry season months, possibly creating favorable bacterial growth conditions. Potentially pathogenic genera were present in the PEI. However their relatively low, non-significant abundance levels highlight their relatively low risk for public health concerns. This study represents the first to sample a large port at this sampling scale and sequencing depth. These data can help establish the inlet microbial community baseline and supplement the vital monitoring of local marine and recreational environments, all the more poignant in context of local reef disease outbreaks and worldwide coral reef collapse in wake of a harsh 2014–16 El Niño event.

Changes in microbial water quality in RAS following altered feed loading

Intensive recirculating aquaculture systems (RAS) with its hyper-eutrophic water offer ideal conditions for bacterial growth, abundance and activity, potentially affecting fish and system performance. Feed composition and feed loading in particular will have significant impact on organic and inorganic nutrients available for microbial growth in RAS. How these nutrient inputs affect and regulate bacteria in RAS water is, however, unclear. To investigate this relationship and the associated water quality dynamics, the effects of altered feed loading on microbial water quality in RAS was studied.The study included six independent, identical pilot-scale RAS, each with a total volume of 1.7 m3 (make-up water: 80 L/day) stocked with juvenile rainbow trout (Oncorhynchus mykiss). All systems had been operating with constant and identical feed loading of 3.13 kg feed/m3 make-up water for a period of three months before the experiment was initiated. Three controlled levels of feed loading where established in duplicates: no feed (0 kg feed/m3), unchanged feeding (3.13 kg feed/m3), and doubled feeding (6.25 kg feed/m3). The experimental period was seven weeks, where microbial and chemical water quality was monitored weekly. Bacterial activity was measured using Bactiquant®, and microbial hydrogen peroxide degradation. Bacterial abundance was quantified by flow cytometry, and water quality parameters by standardized methods The study showed that water quality as well as bacterial activity and abundance were affected by the changes in feed loading. The microbial water quality parameters, however, did not respond to feed loading changes as quickly and straightforward as the physicochemical parameters such as nitrate, chemical oxygen demand and biological oxygen demand. It was presumed that the fixed bed biofilter suppressed microbial response in the water phase. Hydrogen peroxide degradation assay proved to have considerable potential for assessing overall bacterial load in RAS water although further adjustments and standardization procedures are required.

Selective Attachment of Leptospirillum ferrooxidans for Separation of Chalcopyrite and Pyrite through Bio-Flotation

The replacement of depressants used in sulfide mineral beneficiation, with bacteria and their metabolites, promises to reduce the environmental impact left by the mining industry. In this study, the attachment of Leptospirillum ferrooxidans, L.f, to chalcopyrite and pyrite was investigated through Scanning Electron Microscopy (SEM). The impact of selective attachment, bacterial growth conditions, and extracellular polymeric substances (EPS) was investigated through bio-flotation. L.f exhibits selective attachment to pyrite between 0 h and 168 h exposure via an indirect contact mechanism. Separation of chalcopyrite from pyrite was achieved through exposing the minerals for 72 h with an L.f culture grown on either HH media, chalcopyrite, or pyrite. The results produced 80.4, 43.4, and 47.4% recovery of chalcopyrite, respectively. However, EPS supernatant extracted from L.f grown on chalcopyrite, conditioned for 48 h, provided the best separation efficiency by the selective depression of pyrite resulting in 95.8% Cu recovery. Polysaccharide-rich EPS selectively attaches to pyrite within 48 h, depressing its floatability and ensuring successful separation with a PIPX collector.

Staphylococcus aureus Membrane-Derived Vesicles Promote Bacterial Virulence and Confer Protective Immunity in Murine Infection Models.

Staphylococcus aureus produces membrane-derived vesicles (MVs), which share functional properties to outer membrane vesicles. Atomic force microscopy revealed that S. aureus-derived MVs are associated with the bacterial surface or released into the surrounding environment depending on bacterial growth conditions. By using a comparative proteomic approach, a total of 131 and 617 proteins were identified in MVs isolated from S. aureus grown in Luria-Bertani and brain-heart infusion broth, respectively. Purified S. aureus MVs derived from the bacteria grown in either media induced comparable levels of cytotoxicity and neutrophil-activation. Administration of exogenous MVs increased the resistance of S. aureus to killing by whole blood or purified human neutrophils ex vivo and increased S. aureus survival in vivo. Finally, immunization of mice with S. aureus-derived MVs induced production of IgM, total IgG, IgG1, IgG2a, and IgG2b resulting in protection against subcutaneous and systemic S. aureus infection. Collectively, our results suggest S. aureus MVs can influence bacterial–host interactions during systemic infections and provide protective immunity in murine models of infection.

Large-Scale Measurement of mRNA Degradation in Escherichia coli: To Delay or Not to Delay.

In this study, we compared different computational methods used for genome-wide determination of mRNA half-lives in Escherichia coli with a special focus on the impact on considering a delay before the onset of mRNA decay after transcription arrest. A wide variety of datasets were analyzed coming from different technical methods for mRNA quantification (microarrays, RNA-seq, and RT-qPCR) and different bacterial growth conditions. The exponential decay of mRNA levels was fitted using both linear and exponential models and with or without a delay. We showed that for all the models, independently of mRNA quantification methods and growth conditions, ignoring the delay resulted in only a modest overestimation of the half-life. For approximately 80% of the mRNAs, differences in mRNA half-life values were less than 34s. The correlation between half-lives estimated with and without a delay was extremely high. However, the slope of the linear regression between the half-lives with and without a delay tended to decrease with the delay. For the few mRNAs for which taking into account the delay influenced the estimated half-life, the impact was dependent on the model and the growth condition. The smallest impact was obtained for the linear model.