High Bacterial Density Research Articles

Unraveling the in planta population dynamics of the plant pathogen Ralstonia pseudosolanacearum by mathematical modeling.

Ralstonia pseudosolanacearum, a plant pathogen responsible for bacterial wilt in numerous plant species, exhibits paradoxical growth in the host by achieving high bacterial densities in xylem sap, an environment traditionally considered nutrient-poor. This study combined in vitro experiments and mathematical modeling to elucidate the population dynamics of R. pseudosolanacearum within plants. To simulate the xylem environment, a tomato xylem-mimicking medium was developed. Then, a mathematical model was constructed using in vitro data and employed to simulate the dynamics of bacterial density and xylem sap composition during plant infection. The model accurately reproduced in planta experimental observations, including high bacterial densities and the depletion of glutamine and asparagine. Additionally, the model estimated the minimal number of bacteria required to initiate infection, the timing of infection post-inoculation, the bacterial mortality rate within the plant and the rate at which bacterial putrescine is assimilated by the plant. The findings demonstrate that xylem sap can sustain high bacterial densities, provides an explanatory framework for the presence of acetate, putrescine and 3-hydroxybutyrate in the sap of infected xylem and give clues as to the role of putrescine in the virulence of R. pseudosolanacearum.

Fractional-Order Mathematical Modeling of Methicillin- Resistant Staphylococcus aureus Transmission in Hospitals

This article investigates the environmental contamination and antibiotic exposure effect on the transmission dynamics of the Methicillin-Resistant Staphylococcus aureus (MRSA) model in hospitals using the fractional Adams–Bashforth–Moulton Method (ABMM). This epidemic model simulates the dynamics of patient populations, bacterial contamination, and healthcare worker safety under varying conditions. This model provides critical insights into the interactions between hospital practices, environmental factors, and infection dynamics, demonstrating the importance of symmetry in balancing hospital admission and discharge rates to manage infection spread effectively. The analysis extends to the impact of environmental bacterial density and hospital admission rates on patient colonization. Increasing admission rates introduce more susceptible patients, exacerbating infection spread when bacterial density is high. Conversely, lower admission rates and bacterial density result in a more controlled infection environment. The model further investigates how varying discharge rates influence colonization dynamics, highlighting that effective discharge practices can mitigate infection spread, especially in high-bacterial density scenarios. It must be noted that this model is studied fractionally for the first time. Overall, this model provides critical insights into the interactions between hospital practices, environmental factors, and infection dynamics, offering valuable guidance for infection control strategies and hospital policy formulation. By adjusting fractional order constant (σ) values and analyzing different scenarios, this research aids in understanding and managing bacterial infections in healthcare settings. The proposed method is able to provide the results presented in the figures within this study considering the influence of many factors.

Life history traits of the gastropod-associated bacterivorous nematode Caenorhabditis brenneri (Nematoda: Rhabditida)

Abstract. Dalan L, Tañan V, Diano MA, Demayo C, Tabelin M, Sumaya NH. 2024. Life history traits of the gastropod-associated bacterivorous nematode Caenorhabditis brenneri (Nematoda: Rhabditida). Biodiversitas 25: 3106-3113. Caenorhabditis species are associated with decaying plant materials and invertebrates such as terrestrial gastropods. Few Caenorhabditis species have been studied regarding their ecology, genetics, development, and essential life history traits (LHT). In this study, we describe the life cycle of a free-living, wild-type, bacterivorous nematode, Caenorhabditis brenneri Sudhaus and Kiontke 2007, associated with the terrestrial slug Philippinella moellendorffi Collinge 1899 and account for the effects of food density and temperature on its population dynamics by employing the hanging drop technique. The bacterial food supply was sourced from the slug cadaver and identified as Alcaligenes faecalis (MT012081). C. brenneri was fed with varying bacterial densities (109 and 5×109 cells mL-1) and incubated at 20 and 25°C. The bacterial food density-temperature interaction was found to have no significant influence on the offspring production of C. brenneri. Moreover, the total fertility rate (TFR) and net reproductive rate (Ro) are higher in 109 cells mL-1 in both temperatures (TFR at 20°C: 139; 25°C: 169 and Ro at 20°C: 134; 25°C: 156). Whereas the alternative generation time (To, T1, T) and population doubling time (PDT) are faster at 25°C in both bacterial densities, the intrinsic rate of natural increase (rm) is faster at lower temperatures (20°C) in both bacterial densities. The average lifespan of C. brenneri is seven days when fed with A. faecalis. Offspring somatic growth (body length and width) was influenced by bacterial food density-temperature interaction with increased length and girth observed in higher bacterial density and temperature in our knowledge. This study is the first attempt to use A. faecalis, a wild-type bacterium from the terrestrial slug P. moellendorffi cadaver, as the bacterial food source for a Caenorhabditis LHT analysis.

Simplification of the Acidithiobacillus ferrooxidans Culture Process for Expanding the Field of Biomachining.

Biomachining is an eco-friendly metal processing method with broad application potential. Nevertheless, the bacterial culture methods that are currently involved in biomachining require the intensive use of chemical reagents, especially FeSO4, specialized equipment, and professional-level skills in the field of biology. Herein, the differences between two cultures with and without sterilization were evaluated. Acidithiobacillus ferrooxidans was cultured with iron instead of FeSO4 in the culture medium. The chemical and biochemical parameters of the culture were analyzed by studying the area of exposed iron and continuously regulating the pH. Eliminating the sterilization and sterile inoculation of the medium is feasible for culturing A. ferrooxidans. The key to achieving a high bacterial density in culture with iron was to maintain the solution pH. The possibility of mass culturing A. ferrooxidans with steel cuttings was evaluated in a custom bioreactor, and the bacterial concentration reached 9 × 107 cells/mL.

Two-step pH regulating ethanol production through continuous CO/CO2 gas fermentation by mixed bacteria from rabbit faeces

Mixed bacterial syngas fermentation is a promising carbon-neutral method for producing acetic acid and ethanol. However, the bacterial community and metabolic pathways were different in the growth and ethanol production stages, whereas the activity of the bacterial community greatly depended on the pH of the culture. In this study, the effect of pH on syngas fermentation performance and microbial community composition under continuous gas supply was investigated. The mixed bacteria grew fastest at a pH of 7, while a constant pH of 6 led to the highest ethanol concentration of 5.15 g L−1, which was 160 % higher than that at pH 7. Based on this, a two-step pH regulation method was proposed in this study to improve the ethanol production. Initially, the culture pH was maintained at 7 to create optimal growth conditions. Once bacterial density stabilized, it was then changed to a pH 6 to promote ethanol production. By doing this, compared with the control group, the maximum ethanol concentration (5.85 g L−1) increased by 148.9 %, the ethanol production rate (2.41 g L−1 d−1) increased by more than 8 times. This two-step pH regulation method ensured a high bacterial density and effectively stimulated ethanol production during syngas fermentation.

Evidence of Reduced Virulence and Increased Colonization Among Pneumococcal Isolates of Serotype 3 Clade II Lineage in Mice.

Recent phylogenetic profiling of pneumococcal serotype 3 (Pn3) isolates revealed a dynamic interplay among major lineages with the emergence and global spread of a variant termed clade II. The cause of Pn3 clade II dissemination along with epidemiological and clinical ramifications are currently unknown. Here, we sought to explore biological characteristics of dominant Pn3 clades in a mouse model of pneumococcal invasive disease and carriage. Carriage and virulence potential were strain dependent with marked differences among clades. We found that clinical isolates from Pn3 clade II are less virulent and less invasive in mice compared to clade I isolates. We also observed that clade II isolates are carried for longer and at higher bacterial densities in mice compared to clade I isolates. Taken together, our data suggest that the epidemiological success of Pn3 clade II could be related to alterations in the pathogen's ability to cause invasive disease and to establish a robust carriage episode.

Effect of passive particle shape on effective force in active bath

<sec>In active matter, the effective force between passive objects is crucial for their structure and dynamics, which is the basis for understanding the complex behaviors within active systems. Unlike equilibrium states, the factors such as the surface configuration, size, and confinement strength significantly influence the effective forces between passive particles. Previous studies have shown that the shapes of passive particles affect the aggregation of active particles, leading to different forces experienced by passive particles with different shapes. However, recently, a long-range attractive force between passive platelike particles, caused by the bacterial flow field instead of the direct bacterium-plate collisions in active bacterial suspensions, has been found. This raises an intriguing question: how does hydrodynamics affect the forces on passive particles of different shapes in different ways?</sec><sec>In this work, we investigate the effective forces exerted on passive spherical and plate-like particles immersed in bacterial suspensions by optical-tweezers experiments. The effective force between passive particles can be calculated from the formula, <inline-formula><tex-math id="M1">\begin{document}$ {F_{{\text{eff}}}} = {\text{ }}k\left\langle {\Delta d} \right\rangle /2 $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="15-20240650_M1.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="15-20240650_M1.png"/></alternatives></inline-formula>, where <inline-formula><tex-math id="M2">\begin{document}$ \left\langle {\Delta d} \right\rangle $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="15-20240650_M2.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="15-20240650_M2.png"/></alternatives></inline-formula> represents the difference in distance between the passive particles in the bacterial bath and those in the solution without bacteria, <inline-formula><tex-math id="M3">\begin{document}$ k $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="15-20240650_M3.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="15-20240650_M3.png"/></alternatives></inline-formula> is the effective stiffness of optical traps. The <inline-formula><tex-math id="M5">\begin{document}$ {{{F}}}_{{\mathrm{e}}{\mathrm{f}}{\mathrm{f}}} > 0 $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="15-20240650_M5.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="15-20240650_M5.png"/></alternatives></inline-formula> indicates a repulsive force between passive particles, and the <inline-formula><tex-math id="M6">\begin{document}$ {F_{{\text{eff}}}} \lt {\text{ }}0 $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="15-20240650_M6.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="15-20240650_M6.png"/></alternatives></inline-formula> represents an effective attractive force between passive particles. Our results demonstrate that the passive spherical particles experience short-range repulsion, while plate-like particles are subjected to long-range attraction. This highlights the substantial effect of particle shape on their effective forces.</sec><sec>The forces on passive particles are mainly attributed to two factors: direct bacterium-particle collisions and the bacterial flow field. The analysis of the bacterial concentration and orientation distribution around passive particles reveals that for spherical particles, the concentration of bacteria between particles is higher than that outside the particles, but there is almost no difference in the orientation order between bacteria inside and outside the particles. This suggests that the effective repulsion between spherical particles is mainly due to the direct bacterial collisions. Conversely, for plate-like particles, the long-range attraction is primarily influenced by the bacterial flow field rather than their direct collisions, which is evidenced by the higher bacterial density and orientation order inside the two plates compared with those outside the two plates. This study provides strong evidence that the effective force between passive particles is shape dependent in active bath, and offers new insights into controlling active-directed assembly.</sec>

Bacterial diversity associated with the Hatay yellow strain silkworm (Bombyx mori L.): Isolation, identification and characterization

The Hatay yellow strain silkworm (Bombyx mori L.), which is in danger of extinction, is one of the most important local cultural heritages of Türkiye. Bacterial pathogens of silkworm are highly destructive and cause mostly acute diseases. The aim of this study was to determine the bacterial diversity and potential pathogenic bacterial species in infected and dead larvae of Hatay yellow race. A total of 16 bacterial isolates from Hatay yellow race were identified according to their morphological, biochemical and molecular characteristics. The bacterial isolates isolated from infected and dead larvae of Hatay yellow race were Staphylococcus sp. (BM-1), Staphylococcus xylosus (BM-5), Staphylococcus succinus (BM-7), Bacillus thuringiensis (BM-8), Bacillus subtilis (BM-9), Bacillus sp. (BM-10), Staphylococcus saprophyticus (BM-16, BM-19), Klebsiella sp. (BM-17), Staphylococcus arlettae (BM-18), Pseudomonas aeruginosa (BM-20), Enterococcus mundtii (BM-21), Pantoea agglomerans (BM-22), Kluyvera intermedia (BM-23), Serratia sp. (BM-24), Mammaliicoccus sciuri (BM-25). The high bacterial density and number of species indicate that Hatay yellow race is highly susceptible to bacterial diseases. Insecticidal activity studies revealed that species belonging to Bacillus and Staphylococcus genera are important pathogens of hybrid silkworm culture and Hatay yellow race.

Bacillus megaterium RTS1 enhances resistance of Lycopersicon esculentum to salinity stress through the improvement of antioxidant defenses

Background and Objectives: Plant growth-promoting bacteria (PGPB) may reduce the negative effects of salinity stress. The aim of this study was to optimize Bacillus megaterium RTS1 and characterize the effect of the PGPB on the physiolog- ical characteristics of tomato (Lycopersicon esculentum).
 Materials and Methods: The Central composite design (CCD) of response surface methodology (RSM) was used to opti- mize Bacillus megaterium RTS1 to produce maximum cell biomass and spores. Then the effect of the PGPB on the physi- ological characteristics of tomato (Lycopersicon esculentum), including membrane stability, leaf relative water content per- centage, anthocyanin and carotenoids content, chlorophyll photosynthetic parameters, sugar and starch level, superoxide anion and antioxidant activity under salt stress conditions. The NFB medium was inoculated with 5% bacterial culture and the fermentation was carried out in a 10-lit fermenter.
 Results: After optimization, the amount of cell biomass by the model was 9.45 log10 CFUs/mL, which showed a 1.2-fold increase compared to the non-optimized medium. Usage of bacteria under the optimal conditions of the culture medium may increase the stability of the membrane and improve the relative water content. Bacteria were able to prevent the excessive increase of anthocyanins. Oxidative stress led to an increase in the content of chlorophyll a, while causing the degradation of chlorophyll b. Bacterial inoculation led to an increase in the level of sugar and starch compared to the control. PGPB showed an increasing effect on the amount of superoxide anion production and caused a significant increase in the antioxidant activity under salinity stress conditions.
 Conclusion: The PGPB can be a promising way to boost physiological characteristics of tomato plant under salinity stress. Also, sporulation capacity of Bacillus megaterium with high bacterial cell density in fermenter produce a sustainable product for tomato plants.

Hydrodynamics-Induced Long-Range Attraction between Plates in Bacterial Suspensions.

We perform optical-tweezers experiments and mesoscale fluid simulations to study the effective interactions between two parallel plates immersed in bacterial suspensions. The plates are found to experience a long-range attraction, which increases linearly with bacterial density and decreases with plate separation. The higher bacterial density and orientation order between plates observed in the experiments imply that the long-range effective attraction mainly arises from the bacterial flow field, instead of the direct bacterium-plate collisions, which is confirmed by the simulations. Furthermore, the hydrodynamic contribution is inversely proportional to the squared interplate separation in the far field. Our findings highlight the importance of hydrodynamics on the effective forces between passive objects in active baths, providing new possibilities to control activity-directed assembly.

A quaternary ammonium salt grafted tannin-based flocculant boosts the conjugative transfer of plasmid-born antibiotic resistance genes: The nonnegligible side of their flocculation-sterilization properties

This study developed dual-function tannin-based flocculants, namely tannin-graft-acrylamide-diallyl dimethyl ammonium chloride (TGCC-A/TGCC-C), endowed with enhanced flocculation-sterilization properties. The impacts of these flocculants on proliferation and transformation of antibiotic resistance genes (ARGs) among bacteria during the flocculation-deposition process were examined. TGCC-A/TGCC-C exhibited remarkable flocculation capacities towards both Escherichia coli and Staphylococcus aureus, encompassing a logarithmic range of initial cell density (108–109 CFU/mL) and a broad pH spectrum (pH 2–11). The grafted quaternary ammonium salt groups played pivotal parts in flocculation through charge neutralization and bridging mechanisms, concurrently contributing to sterilization by disrupting cellular membranes. The correlation between flocculation and sterilization entails a sequential progression, where an excess of TGCC, initially employed for flocculation, is subsequently consumed for sterilization purposes. The frequencies of ARGs conjugative transfer were enhanced in bacterial flocs across all TGCC treatments, stemming from augmented bacterial aggregation and cell membrane permeability, elicited stress response, and up-regulated genes encoding plasmid transfer. These findings underscore the indispensable role of flocculation-sterilization effects in mediating the propagation of ARGs, consequently providing substantial support for the scientific evaluation of the environmental risks associated with flocculants in the context of ARGs dissemination during the treatment of raw water featuring high bacterial density.

Bacteroides fragilis expresses three proteins similar to Porphyromonas gingivalis HmuY: Hemophore-like proteins differentially evolved to participate in heme acquisition in oral and gut microbiomes.

Oral and gut microbiomes are important for the maintenance of homeostasis in the human body. Altered or disturbed mutualism between their members results in dysbiosis with local injury and subsequent systemic diseases. The high bacterial density causes intense competition among microbiome residents to acquire nutrients, including iron and heme, the latter of high importance for heme auxotrophic members of the Bacteroidetes phylum. Our main hypothesis is that the heme acquisition mechanism, with the leading role played by a novel HmuY family of hemophore-like proteins, can be used to fulfill nutritional requirements and increase virulence. We characterized HmuY homologs expressed by Bacteroides fragilis and compared their properties with the first representative of this family, the HmuY protein of Porphyromonas gingivalis. In contrast to other Bacteroidetes members, B. fragilis produces three HmuY homologs (Bfr proteins). All bfr transcripts were produced at higher levels in bacteria starved of iron and heme (fold change increase ~60, ~90, and ~70 for bfrA, bfrB, and bfrC, respectively). X-ray protein crystallography showed that B. fragilis Bfr proteins are structurally similar to P. gingivalis HmuY and to other homologs, except for differences in the potential heme-binding pockets. BfrA binds heme, mesoheme, and deuteroheme, but preferentially under reducing conditions, using Met175 and Met146 to coordinate heme iron. BfrB binds iron-free protoporphyrin IX and coproporphyrin III, whereas BfrC does not bind porphyrins. HmuY is capable of heme sequestration from BfrA, which might increase the ability of P. gingivalis to cause dysbiosis also in the gut microbiome.

Flagellar-based motility accelerates IgA-mediated agglutination of Salmonella Typhimurium at high bacterial cell densities.

Secretory IgA (SIgA) protects the intestinal epithelium from enteric pathogens such as Salmonella enterica serovar Typhimurium (STm) through a process known as immune exclusion, where invading bacteria are aggregated via antibody cross-linking, encased in mucus, and then cleared from the intestinal tract via peristalsis. At high cell densities, the STm aggregates form a tightly packed network that is reminiscent of early bacterial biofilms. However, the underlying mechanism of how SIgA mediates this transition from a motile and invasive state to an avirulent sessile state in STm is currently unknown. In this report, we developed and validated a methodology known as the "snow globe" assay to enable real-time imaging and quantification of STm agglutination by the mouse monoclonal IgA Sal4. We observed that agglutination in the snow globe assay was dose-dependent, antigen-specific, and influenced by antibody isotype. We determined that flagellar-based motility was a prerequisite for rapid onset of agglutination, even at high cell densities where cell-cell contacts are expected to be frequent. We also investigated the roles of individual cyclic-di-GMP metabolizing enzymes previously implicated in motility and biofilm formation in Sal4 IgA-mediated agglutination. Taken together, our results demonstrate that IgA-mediated agglutination is a dynamic process influenced by bacterial motility and cell-cell collisions. We conclude that the snow globe assay is a viable platform to further decipher the molecular and genetic determinants that drive this interaction.

Growth kinetics and fitness of fluoroquinolone resistant and susceptible Campylobacter jejuni strains of cattle origin.

Human enterocolitis is frequently caused by the Gram-negative microaerobic bacterium Campylobacter jejuni. Macrolides (e.g., erythromycin) and fluoroquinolones (FQs) (e.g., ciprofloxacin) are the preferred antibiotics for the treatment of human campylobacteriosis. Rapid emergence of FQ-resistant (FQ-R) Campylobacter during treatment with FQ antimicrobials is well known to occur in poultry. Cattle is also an important reservoir of Campylobacter for humans, and FQ-R Campylobacter from cattle has become highly prevalent in recent years. Even though the selection pressure may have contributed to the expansion of FQ-R Campylobacter, the actual impact of this factor appears to be rather low. In this study, we examined the hypothesis that the fitness of FQ-R Campylobacter may have also played a role in the rise seen in FQ-R Campylobacter isolates by employing a series of in vitro experiments in MH broth and bovine fecal extract. First, it was shown that FQ-R and FQ-susceptible (FQ-S) C. jejuni strains of cattle origin had comparable growth rates when individually cultured in both MH broth and the fecal extract with no antibiotic present. Interestingly, FQ-R strains had small but statistically significant increases over FQ-S strains in growth in competition experiments performed in mixed cultures with no antibiotic present. Lastly, it was observed that FQ-S C. jejuni strains developed resistance to ciprofloxacin more readily at high initial bacterial cell density (107 CFU/mL) and when exposed to low levels of the antibiotic (2-4 μg/mL) compared with that at a low level of initial bacterial cell density (105 CFU/mL) and exposure to a high level of ciprofloxacin (20 μg/mL) in both MH broth and the fecal extract. Altogether, these findings indicate that even though FQ-R C. jejuni of cattle origin may have a slightly higher fitness advantage over the FQ-S population, the emergence of FQ-R mutants from susceptible strains is primarily dictated by the bacterial cell density and the antibiotic concentration exposed under in vitro condition. These observation may also provide plausible explanations for the high prevalence of FQ-R C. jejuni in cattle production due to its overall fit nature in the absence of antibiotic selection pressure and for the paucity of development of FQ-R C. jejuni in the cattle intestine in response to FQ-treatment, as observed in our recent studies.

Azithromycin alters spatial and temporal dynamics of airway microbiota in idiopathic pulmonary fibrosis.

High bacterial burden in the lung microbiota predicts progression of idiopathic pulmonary fibrosis (IPF). Azithromycin (AZT) is a macrolide antibiotic known to alter the lung microbiota in several chronic pulmonary diseases, and observational studies have shown a positive effect of AZT on mortality and hospitalisation rate in IPF. However, the effect of AZT on the lung microbiota in IPF remains unknown. We sought to determine the impact of a 3-month course of AZT on the lung microbiota in IPF. We assessed sputum and oropharyngeal swab specimens from 24 adults with IPF included in a randomised controlled crossover trial of oral AZT 500 mg 3 times per week. 16S rRNA gene amplicon sequencing and quantitative PCR (qPCR) were performed to assess bacterial communities. Antibiotic resistance genes (ARGs) were assessed using real-time qPCR. AZT significantly decreased community diversity with a stronger and more persistent effect in the lower airways (sputum). AZT treatment altered the temporal kinetics of the upper (oropharyngeal swab) and lower airway microbiota, increasing community similarity between the two sites for 1 month after macrolide cessation. Patients with an increase in ARG carriage had lower bacterial density and enrichment of the genus Streptococcus. In contrast, patients with more stable ARG carriage had higher bacterial density and enrichment in Prevotella. AZT caused sustained changes in the diversity and composition of the upper and lower airway microbiota in IPF, with effects on the temporal and spatial dynamics between the two sites.

IDENTIFICATION OF BACTERIA FROM POST TIN MINING POND AND THEIR ABILITY TO FORM BIOFILMS AT DIFFERENT PH

A number of water quality indicators in the tin post-mined pond of a certain age indicate that the water condition is acidic, low dissolved oxygen content, low cation exchange capacity, and polluted by heavy metals. Restoration of the water quality of post-tin mining pond can use microorganisms as bioremediation agents. Microorganisms live by forming microbial community structures called biofilms. The aims of this study was to identify and find out the optimal pH of biofilm formation biofilm-forming bacteria from post-tin mining pond. The steps of research method was the isolation of bacteria by the spread plate technique, the biofilm formation test by the crystal violet technique, and the identification of bacteria macroscopically, microscopically, and physiologically. The isolation results showed that the highest bacterial density was at station 3 with a total of 8.1x103 cfu/ml. The results of the visualization of biofilm formation find out the A8 isolate at pH 5 with the most concentrated staining, while the highest Optical Density (OD) value for each pH was 0.11245 (pH 3) for A8 bacteria, 0.1901 (pH 5) for I1 bacteria and 0.1901 (pH 5) for A8 bacteria of 0.08945 (pH 7). There were 14 isolated bacterial belonging to the Genus Branhamella, Bacteroides, Aeromonas, Bacillus and Clostridium 08945 (pH 7). Based on identification results, biofilm-forming bacterial isolates from the tin-mining pond of Rebo Village there were 14 isolated bacterial belonging to the Genus Branhamella, Bacteroides, Aeromonas, Bacillus and Clostridium 08945 (pH 7). There were 14 isolated bacterial belonging to the Genus Branhamella, Bacteroides, Aeromonas, Bacillus and Clostridium.

Lung Allograft Microbiome Association with Gastroesophageal Reflux, Inflammation, and Allograft Dysfunction.

Rationale: It remains unclear how gastroesophageal reflux disease (GERD) affects allograft microbial community composition in lung transplant recipients and its impact on lung allograft inflammation and function. Objectives: Our objective was to compare the allograft microbiota in lung transplant recipients with or without clinically diagnosed GERD in the first year after transplant and assess associations between GERD, allograft microbiota, inflammation, and acute and chronic lung allograft dysfunction (ALAD and CLAD). Methods: A total of 268 BAL samples were collected from 75 lung transplant recipients at a single transplant center every 3 months after transplant for 1 year. Ten transplant recipients from a separate transplant center provided samples before and after antireflux Nissen fundoplication surgery. Microbial community composition and density were measured using 16S ribosomal RNA gene sequencing and quantitative polymerase chain reaction, respectively, and inflammatory markers and bile acids were quantified. Measurements and Main Results: We observed a range of allograft community composition with three discernible types (labeled community state types [CSTs] 1-3). Transplant recipients with GERD were more likely to have CST1, characterized by high bacterial density and relative abundance of the oropharyngeal colonizing genera Prevotella and Veillonella. GERD was associated with more frequent transitions to CST1. CST1 was associated with lower inflammatory cytokine concentrations than pathogen-dominated CST3 across the range of microbial densities observed. Cox proportional hazard models revealed associations between CST3 and the development of ALAD/CLAD. Nissen fundoplication decreased bacterial load and proinflammatory cytokines. Conclusions: GERD was associated with a high bacterial density, Prevotella- and Veillonella-dominated CST1. CST3, but not CST1 or GERD, was associated with inflammation and early development of ALAD and CLAD. Nissen fundoplication was associated with a reduction in microbial density in BAL fluid samples, especially the CST1-specific genus, Prevotella.

Optimization of Agrobacterium tumefaciens-mediated Transformation in Oxalis corniculata (L.)

Background: Optimization of co-cultivation parameters during Agrobacterium-mediated transformation to Oxalis corniculata evaluated were bacterial density, infection period, acetosyringone (AS) concentration and co-cultivation temperature. Five fold transformation efficiency is achieved in transient gus gene expression after optimizing various parameters. The optimized conditions were Agrobacterium tumefaciens growth phase of A600nm 0.17, infection period of 30 min, addition of acetosyringone (AS) in co-cultivation medium (400 μM) and cocultivation temperature of 22°C. Methods: Oxalis corniculata (L.) were used for transformation. Bacterial culture was added to 50 ml of liquid YEP medium with kanamycin and rifampicin and grown until reaching the growth phase (A600nm). Bacterial density ranged from A600nm 0.17, 0.56,0.80 and 1.34 OD were used in the present study. The co-cultivation medium made of solid MS medium consisted of BAP 2 mg L-1 and NAA 0.5 mg L-1 and various concentrations of AS at 0, 50, 100, 200, 400,600 and 800 μM. Histochemical analysis of gene expression was carried out. Result: Higher bacterial density resulted in more transformation efficiency, but also higher necrosis in the explants. Dilution of bacterial suspension reduced necrosis in explants and resulted in higher transformation. The transformation efficiency is 64% when the infection process was carried out with acetosyringone in co-cultivation medium (400 μM). Our studies proved that among the optimized conditions, cocultivation temperature and acetosyringone were the critical parameters during Agrobacterium mediated transformation.

The mechanism by which Enteromorpha Linza polysaccharide promotes Bacillus subtilis growth and nitrate removal

In this study, we discussed the relationship between Entermorpha linza polysaccharide (EP) and Bacillus subtilis, which can transform nitrate. A sole carbon source experiment showed that Bacillus subtilis could utilize EP, and the bacterial density was maximally increased by 54.43% in the EP groups. The results of reducing sugar determination proved the secretion of polysaccharide-degrading enzymes. Scanning electron microscopy (SEM) showed that the EP groups had fewer spores and shrunken bacteria, indicating that EP could improve the growth environment and maintain bacterial integrity. Additionally, the ratios of periplasmic nitrate reductase (NAP), nitrite reductase (NIR), and dissimilatory nitrate reductase (D-NRase) in the EP groups were maximally increased by 107.22%, 84.70% and 36.10%, respectively. Transcriptome analysis further confirmed the above mentioned results. For example, the high expression of quorum sensing genes indicated that EP groups had higher bacterial density. Moreover, the high expression of antioxidant genes in the EP groups may be related to morphological integrity. Our study provides a basis for further discussion of the mechanism.

Quorum Sensing Regulates Bacterial Processes That Play a Major Role in Marine Biogeochemical Cycles

Bacteria play a crucial role in marine biogeochemistry by releasing, consuming and transforming organic matter. Far from being isolated entities, bacteria are involved in numerous cell–cell interactions. Among such interactions, quorum sensing (QS) allows bacteria to operate in unison, synchronizing their actions through chemical communication. This review aims to explore and synthesize our current knowledge of the involvement of QS in the regulation of bacterial processes that ultimately impact marine biogeochemical cycles. We first describe the principles of QS communication and the renewed interest in its study in marine environments. Second, we highlight that the microniches where QS is most likely to occur due to their high bacterial densities are also hotspots of bacterially mediated biogeochemical transformations. Many bacterial groups colonizing these microniches harbor various QS systems. Thereafter, we review relevant QS-regulated bacterial processes in marine environments, building on research performed in both complex marine assemblages and isolated marine bacteria. QS pathways have been shown to directly regulate organic matter degradation, carbon allocation and nutrient acquisition but also to structure the community composition by mediating colonization processes and microbial interactions. Finally, we discuss current limitations and future perspectives to better characterize the link between QS expression and the bacterial mediation of biogeochemical cycles. The picture drawn by this review highlights QS as one of the pivotal mechanisms impacting microbial composition and functions in the oceans, paving the way for future research to better constrain its impact on marine biogeochemical cycles.