Survival of Bacillus spp. SUBB01 at high temperatures and a preliminary assessment of its ability to protect heat-stressed Escherichia coli cells

Interaction and effects of temperature preference under a controlled environment on the diversity and abundance of the microbiome in Lutzomyia longipalpis (Diptera: Psychodidae)

Characterization of the temperature effects on the abundance and richness of the microbiota of Lutzomyia longipalpis, insect vector of Leishmania infantum in America, is an aspect of pivotal importance to understand the interactions between temperature, bacteria, and Leishmania infection. We developed and used a customized device with a temperature gradient (21-34 °C) to assess the temperature preferences of wild females of Lu. longipalpis collected in a rural area (Ricaurte, Cundinamarca, Colombia). Each replicate consisted of 50 females exposed to the gradient for an hour. At the end of the exposure time, insects were collected and separated by the temperature ranges selected varying from 21 °C to 34 °C. They were organized in 17 pools from which total DNA extracts were obtained, and samples were subjected to 16S rRNA amplicon sequencing analyzes. The most abundant phyla across the different temperature ranges were Proteobacteria (17.22-90.73 %), Firmicutes (5.99-77.21 %) and Actinobacteria (1.56-59.85 %). Results also showed an abundance (30 % to 57.36 %) of Pseudomonas (mainly at temperatures of 21-29 °C and 34 °C) that decreased to 6.55 %-13.20 % at temperatures of 31-33 °C, while Bacillus increase its abundance to 67.24 % at 29-33 °C. Serratia also had a greater representation (49.79 %), specifically in sand flies recovered at 25-27 °C. No significant differences were found at α-diversity level when comparing richness using the Shannon-Wiener, Simpson, and Chao1 indices, while β-diversity differences were found using the Bray-Curtis index (F-value of 3.5073, p-value < 0.013, R-squared of 0,4889), especially in the groups of Lu. longipalpis associated at higher temperatures (29-33 °C). It was also possible to detect the presence of endosymbionts such as Spiroplasma and Arsenophonus in the range of 29-33 °C. Rickettsia was only detected in Lu. longipalpis sand flies recovered between 25-27 °C. It was possible to characterize Lu. longipalpis microbiota in response to intraspecific temperature preferences and observe changes in bacterial communities and endosymbionts at different ranges of said environmental variable, which may be important in its vector competence and environmental plasticity to adapt to new climate change scenarios.

Expanding the microbiologist toolbox via new far-red-emitting dyes suitable for bacterial imaging

IMPORTANCE

By harnessing the versatility of fluorescence microscopy and super-resolution imaging, bacteriologists explore critical aspects of bacterial physiology and resolve bacterial structures sized beyond the light diffraction limit. These techniques are based on fluorophores with profitable photochemical and tagging properties. The paucity of available far-red (FR)-emitting dyes for bacterial imaging strongly limits the multicolor choice of bacteriologists, hindering the possibility of labeling multiple structures in a single experiment. The set of FR fluorophores characterized in this study expands the palette of dyes useful for microbiologists, as they can be used for bacterial LIVE/DEAD staining and for tagging the membranes of viable Escherichia coli and Bacillus subtilis cells. The absence of toxicity makes these dyes suitable for live-cell imaging and allows monitoring of bacterial membrane biogenesis. Moreover, a newly synthesized FR-fluorophore can be employed for imaging bacterial membranes with stimulated emission depletion microscopy, a super-resolution technique capable of increasing the resolving power of conventional microscopes.

Probiotic characterization of Bacillus species strains isolated from an artisanal fermented milk product Dahi

Dahi, an artisanal fermented milk product, widely consumed in Pakistan, is microbiologically diverse, and many bacterial communities await investigation. The current study is first to present probiotic assessment of Bacillus species strains isolated from dahi. Based on 49 identified strains assessed, only 6 strains, i.e., Bacillus licheniformis QAUBL19, QAUBL1901, and QAUBL1902; Bacillus mycoides QAUBM19 and QAUBM1901; and Bacillus subtilis QAUBSS1 were having prominent persistence in the simulated gastrointestinal fluids, being non-hemolytic, with no DNase activity. Probiotic characteristics, cholesterol-assimilating, and carbohydrate-fermenting capabilities were assessed for all the strains. These six strains each showed variant cholesterol assimilating abilities. B. licheniformis QAUBL19 retaining most desired probiotic traits presented both notable cholesterol assimilating and bile salt hydrolase activities. It can be used as a probiotic of choice with hypocholesterolemia ability. B. subtilis QAUBSS1 showed wide carbohydrate fermentation ability and strongest antibacterial potential. It is likely to be considered a probiotic for living beings and starter culture for fermentation of food/feed.

Screening and isolation of microbes from a Mud Community of Ischia Island Thermal Springs: preliminary analysis of a bioactive compound

Introduction

Balneotherapy centers of Ischia island (Italy) offer treatments for different dermatological diseases (psoriasis, acne, atopic dermatitis) and upper respiratory tract infections. In this study, we integrated morphological and molecular approaches to give a focus on isolation and screening of extremophile bacteria from Ischia thermal mud for potential antimicrobial applications.

Methods

Samples were collected during 2019 at four sites. Some bacterial strains ATCC for antibacterial and antibiofilm activity were tested. After morphological characterization, screening for antagonistic isolates was made. The colonies isolated from thermal mud samples were submitted to molecular characterization. Susceptibility testing by dilution spotting was carried out and antibacterial efficacies of most active isolate were evaluated with a Minimal inhibition concentration assay. Biofilm formation, inhibition, eradication were examined. Statistical analyses were carried out utilizing Microsoft^® Excel 2016/XLSTAT^©-Pro.

Results

We isolated a natural compound with antimicrobial and antibiofilm activities.

Conclusions

The results obtained in this study are discussed in the context of how hydrothermal systems are important environmental source of uncharted antimicrobial and antibiofilm compounds. In conclusion, to the most effective of our knowledge, this work presents the primary report on the preliminary investigation of thermophile microbial diversity and their antimicrobial and antibiofilm activities for future biotechnological interest.

Increase in temperature enriches heat tolerant taxa in Aedes aegypti midguts

Insect midgut microbial symbionts have been considered as an integral component in thermal adaptation due to their differential thermal sensitivity. Altered midgut microbial communities can influence both insect physiology and competence for important vector-borne pathogens. This study sought to gain insights into how Aedes aegypti midgut microbes and life history traits are affected by increase in baseline diurnal temperature. Increase in temperature resulted in the enrichment of specific taxa with Bacillus being the most enriched. Bacillus is known to be heat tolerant. It also resulted in a dissimilar microbial assemblage (Bray-Curtis Index, PERMANOVA, F = 2.2063; R2 = 0.16706; P = 0.002) and reduced survivorship (Log-rank [Mantel-Cox] test, Chi-square = 35.66 df = 5, P < 0.0001). Blood meal intake resulted in proliferation of pathogenic bacteria such as Elizabethkingia in the midgut of the mosquitoes. These results suggest that alteration of temperature within realistic parameters such as 2 °C for Ae. aegypti in nature may impact the midgut microbiome favoring specific taxa that could alter mosquito fitness, adaptation and vector-pathogen interactions.

Molecular identification of a Bacillus cereus strain from Murrah buffalo milk showed in vitro bioremediation properties on selective heavy metals

Objective:

This study aims for molecular identification of naturally growing Bacillus cereus strain from a unique source, able to survive, and alleviate heavy metals from the nature.

Materials and Methods:

Pure isolate from Murrah buffalo milk was prepared in B. cereus selective Polymyxin pyruvate egg-yolk mannitol–bromothymol blue agar (PEMBA) medium through a cascade of contamination free subcultures. The morphological and biochemical tests were done prior to 16S rRNA gene sequencing for strain identification and further physiological tests. The test strain was inoculated in both solid and suspension culture medium supplemented individually with Cd, Cu, Ag, and Zn to reveal the qualitative and quantitative heavy metal tolerance properties, respectively. Finally, the data collected from the in vitro assessment was statistically analyzed

Results:

Molecular analysis revealed that the test strain was B. cereus BF2, which was motile, catalase positive and Gram positive rod. B. cereus BF2 was found significant at 0.3% bile salt tolerance [two-way analysis of variance (ANOVA)—p value is < 0.0001] where, t-test p value is < 0.0002 between Control Group (CG) and TGR-1; p < 0.037 between TGR-1 and 2; p < 0.0014 between CG and TGR-2. Similarly, B. cereus BF2 was significant in pH tolerant up to 8.0 with p < 0.0115 (in scale p < 0.05). The heavy metal tolerance test revealed that the test metals could not stop the growth of B. cereus BF2 even after 24 h of incubation but partially suppressed the growth kinetics for letting into stationary phase. Among the four heavy metals, Cd and Zn showed partial antagonism to the growth of B. cereus BF2. The survivability was highly significant in the medium supplemented with Zn (p < 0.0001) and Ag (p < 0.018).

Conclusion:

Bacillus cereus BF2 can survive in selective heavy metals with metal resistance and biodegradation capacity.