Regulation of Bioluminescence in Photobacterium leiognathi Strain KNH6

Photorhabdus lux-operon heat shock-like regulation

For decades, transcription of Photorhabdus luminescens lux-operon was considered being constitutive. Therefore, this lux-operon has been used for measurements in non-specific bacterial luminescent biosensors. Here, the expression of Photorhabdus lux-operon under high temperature was studied. The expression was researched in the natural strain Photorhabdus temperata and in the heterologous system of Escherichia coli. P. temperata FV2201 bacterium was isolated from soil in the Moscow region (growth optimum 28 °C). We showed that its luminescence significantly increases when the temperature rises to 34 °C. The increase in luminescence is associated with an increase in the transcription of luxCDABE genes, which was confirmed by RT-PCR. The promoter of the lux-operon of the related bacterium P. luminescens ZM1 from the forests of Moldova, being cloned in the heterologous system of E. coli, is activated when the temperature rises from room temperature to 42 °C. When heat shock is caused by ethanol addition, transcription of lux-operon increases only in the natural strain of P. temperata, but not in the heterologous system of E. coli cells. In addition, the activation of the lux-operon of P. luminescens persists in E. coli strains deficient in both the rpoH and rpoE genes. These results indicate the presence of sigma 32 and sigma 24 independent heat-shock-like mechanism of regulation of the lux-operon of P. luminescens in the heterologous E. coli system.

Photobacterium arenosum WH24, Isolated from the Gill of Pacific Oyster Crassostrea gigas from the North Sea of Germany: Co-cultivation and Prediction of Virulence

Cream colored bacteria from marine agar, strain WH24, WH77, and WH80 were isolated from the gill of the Crassostrea gigas a Pacific oyster with a filter-feeding habit that compels accompanying bacteria to demonstrate a high metabolic capacity, has proven able to colonize locations with changing circumstances. Based on the 16S rRNA gene sequence, all strains had high similarity to Photobacterium arenosum CAU 1568^T (99.72%). This study involved phenotypic traits, phylogenetic analysis, antimicrobial activity evaluation, genome mining, Co-cultivation experiments, and chemical studies of crude extracts using HPLC and LC-HRESIMS. Photobacterium arenosum WH24 and Zooshikella harenae WH53^Twere co-cultivated for 3 days in a rotary shaker at 160 rpm at 30 °C, and LC-MS monitored the chemical profiles of the co-cultures on the third day. The UV chromatograms of the extracts of the co-cultivation experiments show that Zooshikella harenae WH53^T could be inhibited by strain WH24. The high virulence of Photobacterium arenosum WH24 was confirmed by genome analysis. Gene groups with high virulence potential were detected: tssA (ImpA), tssB (ImpB/vipA), tssC (ImpC/vipB), tssE, tssF (ImpG/vasA), tssG (ImpH/vasB), tssM (IcmF/vasK), tssJ (vasD), tssK (ImpJ/vasE), tssL (ImpK/vasF), clpV (tssH), vasH, hcp, lapP, plpD, and tpsB family.

Effects of crude oil and aromatic compounds on growth and bioluminescence of Vibrio campbellii FS5

Fifteen native luminescent bacteria were isolated from the Gulf of Thailand, and their sensitivity for the detection of toxicity of crude oil and its aromatic components was investigated. Of these isolates, Vibrio campbellii strain FS5 was one of the two most highly inhibited bacteria at all crude oil concentrations. This bacterium showed a decrease in luminescence intensity of between 10.7 and 80.2% after a 15-min exposure to 0.0001-10 mg/L of crude oil. The degree of bioluminescence inhibition increased with increasing concentrations of crude oil. The presence of crude oil at all concentrations had negative effects on the log bioluminescence per log number of viable cells after 15- to 105-min exposure. About 10 to 100 times, lower half maximal effective concentration (EC₅₀) values were observed for polycyclic aromatic hydrocarbons (PAHs) than those for benzene, toluene, ethylbenzene, and xylene (BTEX). In the presence of each individual BTEX and PAH, the bioluminescence inhibition increased with increasing exposure time (1-32 h). This indigenous bacterium can be used as a simple and general indicator of oil contamination and its impact on coastal waters as well as for assessing potential toxicity during oil bioremediation.

Cell activity evaluation during bacterial bioluminescence oscillation

Oscillation in bacterial bioluminescence from Photobacterium kishitanii liquid culture was examined regarding reproducibility and bacterial cell activities, i.e., dissolved oxygen (DO) consumption, esterase activity, and product production rate. A frequent increase in DO was suspected to be due to a rapid decrease in luminescence, and a simple model describing not only the monotonous decrease in cell activity, but also the luminescence-DO relationship is proposed.

An Intact Cell Bioluminescence-Based Assay for the Simple and Rapid Diagnosis of Urinary Tract Infection

Urinary tract infection (UTI) is one of the most common infections, accounting for a substantial portion of outpatient hospital and clinic visits. Standard diagnosis of UTI by culture and sensitivity can take at least 48 h, and improper diagnosis can lead to an increase in antibiotic resistance following therapy. To address these shortcomings, rapid bioluminescence assays were developed and evaluated for the detection of UTI using intact, viable cells of Photobacterium mandapamensis USTCMS 1132 or previously lyophilized cells of Photobacterium leiognathi ATCC 33981™. Two platform technologies-tube bioluminescence extinction technology urine (TuBETUr) and cellphone-based UTI bioluminescence extinction technology (CUBET)-were developed and standardized using artificial urine to detect four commonly isolated UTI pathogens-namely, Escherichia coli, Proteus mirabilis, Staphylococcus aureus, and Candida albicans. Besides detection, these assays could also provide information regarding pathogen concentration/level, helping guide treatment decisions. These technologies were able to detect microbes associated with UTI at less than 105 CFU/mL, which is usually the lower cut-off limit for a positive UTI diagnosis. Among the 29 positive UTI samples yielding 105-106 CFU/mL pathogen concentrations, a total of 29 urine specimens were correctly detected by TuBETUr as UTI-positive based on an 1119 s detection window. Similarly, the rapid CUBET method was able to discriminate UTIs from normal samples with high confidence (p ≤ 0.0001), using single-pot conditions and cell phone-based monitoring. These technologies could potentially address the need for point-of-care UTI detection while reducing the possibility of antibiotic resistance associated with misdiagnosed cases of urinary tract infections, especially in low-resource environments.

Bioluminescent method for the rapid screening of toxic heayy metals in environmental samples using Photobacterium leiognathi strain AK-MIE

Assessment of eco-toxicant using bioluminescent bacterial assay is a widely used and globally accepted method. In this work, a new luminescent bacterium was isolated from squid (Loligo duvauceli) and identified as Photobacterium leiognathi strain AK-MIE using 16S rRNA, phylogeny analysis. The predicted optimum conditions by RSM were 2.76% (w/v) NaCl, 2.28% (w/v) peptone, 0.34% (w/v) yeast extract, and pH 6.83 with 541,211.80 RLU of luminescent production whereas the predicted optimum conditions by ANN were 2.21% (w/v) NaCl, 2.27% (w/v) peptone, 0.39% (w/v) yeast extract, and pH 6.94 which produced 541,986.20 RLU. The validation analysis of both RSM and ANN show 0.60% and 0.69% deviation from the predicted results indicating that both models provided good quality predictions with ANN showing a superior data fitting capability for non-linear regression analysis. Toxicity tests show strain AK-MIE was sensitive to mercury (concentration causing 50% inhibition or IC₅₀ of 0.00978 mgL^-1), followed by cadmium (IC₅₀ of 0.5288 mgL^-1), copper IC₅₀ of (0.8117 mgL^-1), silver (IC₅₀ of 1.109 mgL^-1), and lead (IC₅₀ of 10.71 mgL^-1) which are more sensitive than previously isolated luminescent bacteria, suggesting that strain AK-MIE has the potential to be used in toxicity assessment of heavy metals in the environment. Based on the field trial results, several sediment samples from industrial areas in Bangi, Selangor managed to inhibit the bioluminescence of strain AK-MIE. Validation method carried out using ICP-MS proved the presence of several toxic heavy metal elements.

Recycled low-density polyethylene composite to mitigate the environmental impacts generated from coal mining waste in Brazil

Waste materials from coal mining and consumer products can pose significant risks to the environment. Residual coal deposits lead to the formation of acid drainage and release of contaminants, causing negative changes in soil and aquatic systems. Low density polyethylene (LDPE) polymers are an environmental concern due to their high useage, and slow degradation in the environment. In this study both waste materials were used to develop a composite to mitigate the environmental impacts of coal mining waste (CMW). The composite material was produced in different formulations (0-80 % wt CMW), and samples were tested for formation of acid drainage and release of contaminants. Chemical characterisation of the CMW and leachate of the composite materials was performed by X-ray fluorescence and atomic absorption spectrometry. Ecotoxicological effects in soil and water were investigated using standard tests with the earthworm, Eisenia fetida, the collembolan, Folsomia candida and the bacterium, Aliivibrio fischeri. Composites with 20 % wt LDPE showed a 50% increase in the pH value of the leachate compared to the CMW leachate. Iron, aluminium and sulfate concentrations were lower in leachates of the composite materials, and a reduction in the ecotoxicological impact on the tested organisms was observed. The hydrophobic nature of the composite's polymeric matrix as well its physical properties contributed to a better coating of the coal residue particles, blocking the contact with water and reducing the environmental risks of CMW. These results show that the production of composite material is a viable alternative route for treating coal and LDPE waste.

Soluble electron acceptors affect bioluminescence from Shewanella woodyi

Shewanella woodyi cultures were used to correlate bioluminescence intensity with changes in the electrochemical potential of a saltwater medium using soluble electron acceptors. A relationship between the concentration of NaNO₃ or CoCl₂ to bioluminescence intensity was confirmed using aerobic cultures of S. woodyi at 20°C with glucose as the sole carbon source. In general, increasing the concentration of nitrate or Co(II) reduced the bioluminescence per cell, with complete luminescence being repressed at ≥5 mM nitrate and ≥0.5 mM Co(II). Results from cell viability fluorescent staining concluded that increasing the concentration of Co(II) or nitrate did not affect the overall viability of the cells when compared with cultures lacking Co(II) or nitrate. These data show that potentials of <0.2 V vs Normal Hydrogen Electrode (NHE) repress the luminescence from the cells, but the exact mechanism is unclear. Our results indicated that the luminescence intensity from S. woodyi could be systematically reduced using these two soluble electron acceptors, making S. woodyi a potential model bacterium for whole-cell luminescence bioelectrochemical sensor applications.

Ambient pH Alters the Protein Content of Outer Membrane Vesicles, Driving Host Development in a Beneficial Symbiosis

Outer membrane vesicles (OMVs) are continuously produced by Gram-negative bacteria and are increasingly recognized as ubiquitous mediators of bacterial physiology. In particular, OMVs are powerful effectors in interorganismal interactions, driven largely by their molecular contents. These impacts have been studied extensively in bacterial pathogenesis but have not been well documented within the context of mutualism. Here, we examined the proteomic composition of OMVs from the marine bacterium Vibrio fischeri, which forms a specific mutualism with the Hawaiian bobtail squid, Euprymna scolopes We found that V. fischeri upregulates transcription of its major outer membrane protein, OmpU, during growth at an acidic pH, which V. fischeri experiences when it transitions from its environmental reservoir to host tissues. We used comparative genomics and DNA pulldown analyses to search for regulators of ompU and found that differential expression of ompU is governed by the OmpR, H-NS, and ToxR proteins. This transcriptional control combines with nutritional conditions to govern OmpU levels in OMVs. Under a host-encountered acidic pH, V. fischeri OMVs become more potent stimulators of symbiotic host development in an OmpU-dependent manner. Finally, we found that symbiotic development could be stimulated by OMVs containing a homolog of OmpU from the pathogenic species Vibrio cholerae, connecting the role of a well-described virulence factor with a mutualistic element. This work explores the symbiotic effects of OMV variation, identifies regulatory machinery shared between pathogenic and mutualistic bacteria, and provides evidence of the role that OMVs play in animal-bacterium mutualism.IMPORTANCE Beneficial bacteria communicate with their hosts through a variety of means. These communications are often carried out by a combination of molecules that stimulate responses from the host and are necessary for development of the relationship between these organisms. Naturally produced bacterial outer membrane vesicles (OMVs) contain many of those molecules and can stimulate a wide range of responses from recipient organisms. Here, we describe how a marine bacterium, Vibrio fischeri, changes the makeup of its OMVs under conditions that it experiences as it goes from its free-living lifestyle to associating with its natural host, the Hawaiian bobtail squid. This work improves our understanding of how bacteria change their signaling profile as they begin to associate with their beneficial partner animals.

Bacterial Bioluminescence: Light Emission in Photobacterium phosphoreum Is Not Under Quorum-Sensing Control

Bacterial-bioluminescence regulation is often associated with quorum sensing. Indeed, many studies have been made on this subject and indicate that the expression of the light-emission-involved genes is density dependent. However, most of these studies have concerned two model species, Aliivibrio fischeri and Vibrio campbellii. Very few works have been done on bioluminescence regulation for the other bacterial genera. Yet, according to the large variety of habitats of luminous marine bacteria, it would not be surprising to find different light-regulation systems. In this study, we used Photobacterium phosphoreum ANT-2200, a piezophilic bioluminescent strain isolated from Mediterranean deep-sea waters (2200-m depth). To answer the question of whether or not the bioluminescence of P. phosphoreum ANT-2200 is under quorum-sensing control, we focused on the correlation between growth and light emission through physiological, genomic and, transcriptomic approaches. Unlike A. fischeri and V. campbellii, the light of P. phosphoreum ANT-2200 immediately increases from its initial level. Interestingly, the emitted light increases at much higher rate at the low cell density than it does for higher cell-density values. The expression level of the light-emission-involved genes stays constant all along the exponential growth phase. We also showed that, even when more light is produced, when the strain is cultivated at high hydrostatic pressure, no change in the transcription level of these genes can be detected. Through different experiments and approaches, our results clearly indicate that, under the tested conditions, the genes, directly involved in the bioluminescence in P. phosphoreum ANT-2200, are not controlled at a transcriptomic level. Quite obviously, these results demonstrate that the light emission of the strain is not density dependent, which means not under quorum-sensing control. Through this study, we point out that bacterial-bioluminescence regulation should not, from now on, be always linked with the quorum-sensing control.

Mutagenesis of Vibrio fischeri and Other Marine Bacteria Using Hyperactive Mini-Tn5 Derivatives

Mutagenizing bacterial genomes with selectable transposon insertions is an effective approach for identifying the genes underlying important phenotypes. Specific bacteria may require different tools and methods for effective transposon mutagenesis, and here we describe methods to mutagenize Vibrio fischeri using an engineered mini-Tn5 transposon with synthetic "mosaic" transposon ends. The transposon is delivered by conjugation on a plasmid that cannot replicate in V. fischeri and that encodes a hyperactive transposase outside the transposon itself. The chromosomal location of insertions can be readily identified by cloning and/or PCR-based methods described here. Although developed in V. fischeri, these tools and methods have proven effective in some other bacteria as well.

Vibrio fischeri bioluminescence inhibition assay for ecotoxicity assessment: A review

Vibrio fischeri bioluminescence inhibition bioassay (VFBIA) has been widely applied for the monitoring of toxicity on account of multiple advantages encompassing shorter test duration, sensitive, cost-effective and ease of operation. Moreover, this bioassay found to be equally applicable to all types of matrices (organic & inorganic compounds, metals, wastewater, river water, sewage sludge, landfill leachate, herbicides, treated wastewater etc.) for toxicity monitoring. This review highlights the apparent significance of Vibrio fischeri bioluminescence inhibition assay for ecotoxicological screening and evaluation of diverse chemical substances toxicity profile. The biochemical and genetic basis of the bioluminescence assay and its regulatory mechanism have been concisely discussed. The basic test protocol with ongoing improvements, widespread applications, typical advantages and probable limitations of the assay have been overviewed. The sensitivity of VFBIA and toxicity bioassays has also been compared.

Physiological Translocation of Lactic Acid Bacteria during Pregnancy Contributes to the Composition of the Milk Microbiota in Mice

The human milk microbiota is a complex and diverse ecosystem that seems to play a relevant role in the mother-to-infant transmission of microorganisms during early life. Bacteria present in human milk may arise from different sources, and recent studies suggest that at least some of them may be originally present in the maternal digestive tract and may reach the mammary gland through an endogenous route during pregnancy and lactation. The objective of this work was to elucidate whether some lactic acid bacteria are able to translocate and colonize the mammary gland and milk. For this purpose, two lactic acid bacteria strains (Lactococcus lactis MG1614 and Lactobacillus salivarius PS2) were transformed with a plasmid containing the lux genes; subsequently, the transformed strains were orally administered to pregnant mice. The murine model allowed the visualization, isolation, and Polymerase Chain Reaction (PCR)-detection of the transformed bacteria in different body locations, including mammary tissue and milk, reinforcing the hypothesis that physiological translocation of maternal bacteria during pregnancy and lactation may contribute to the composition of the mammary and milk microbiota.