Bacterial Compounds Research Articles

A Comparative Study on Repairing of Binding Material Discontinuity Using Cultured Bacterial Compounds

A Comparative Study on Repairing of Binding Material Discontinuity Using Cultured Bacterial Compounds

Rhizobacterium‐derived diacetyl modulates plant immunity in a phosphate‐dependent manner

Plants establish mutualistic associations with beneficial microbes while deploying the immune system to defend against pathogenic ones. Little is known about the interplay between mutualism and immunity and the mediator molecules enabling such crosstalk. Here, we show that plants respond differentially to a volatile bacterial compound through integral modulation of the immune system and the phosphate‐starvation response (PSR) system, resulting in either mutualism or immunity. We found that exposure of Arabidopsis thaliana to a known plant growth‐promoting rhizobacterium can unexpectedly have either beneficial or deleterious effects to plants. The beneficial‐to‐deleterious transition is dependent on availability of phosphate to the plants and is mediated by diacetyl, a bacterial volatile compound. Under phosphate‐sufficient conditions, diacetyl partially suppresses plant production of reactive oxygen species (ROS) and enhances symbiont colonization without compromising disease resistance. Under phosphate‐deficient conditions, diacetyl enhances phytohormone‐mediated immunity and consequently causes plant hyper‐sensitivity to phosphate deficiency. Therefore, diacetyl affects the type of relation between plant hosts and certain rhizobacteria in a way that depends on the plant's phosphate‐starvation response system and phytohormone‐mediated immunity.

The ecological role of bacterial seed endophytes associated with wild cabbage in the United Kingdom.

Endophytic bacteria are known for their ability in promoting plant growth and defense against biotic and abiotic stress. However, very little is known about the microbial endophytes living in the spermosphere. Here, we isolated bacteria from the seeds of five different populations of wild cabbage (Brassica oleracea L) that grow within 15 km of each other along the Dorset coast in the UK. The seeds of each plant population contained a unique microbiome. Sequencing of the 16S rRNA genes revealed that these bacteria belong to three different phyla (Actinobacteria, Firmicutes, and Proteobacteria). Isolated endophytic bacteria were grown in monocultures or mixtures and the effects of bacterial volatile organic compounds (VOCs) on the growth and development on B. oleracea and on resistance against a insect herbivore was evaluated. Our results reveal that the VOCs emitted by the endophytic bacteria had a profound effect on plant development but only a minor effect on resistance against an herbivore of B. oleracea. Plants exposed to bacterial VOCs showed faster seed germination and seedling development. Furthermore, seed endophytic bacteria exhibited activity via volatiles against the plant pathogen F. culmorum. Hence, our results illustrate the ecological importance of the bacterial seed microbiome for host plant health and development.

Unusual Metabolism and Hypervariation in the Genome of a Gracilibacterium (BD1-5) from an Oil-Degrading Community.

The candidate phyla radiation (CPR) comprises a large monophyletic group of bacterial lineages known almost exclusively based on genomes obtained using cultivation-independent methods. Within the CPR, Gracilibacteria (BD1-5) are particularly poorly understood due to undersampling and the inherent fragmented nature of available genomes. Here, we report the first closed, curated genome of a gracilibacterium from an enrichment experiment inoculated from the Gulf of Mexico and designed to investigate hydrocarbon degradation. The gracilibacterium rose in abundance after the community switched to dominance by Colwellia Notably, we predict that this gracilibacterium completely lacks glycolysis, the pentose phosphate and Entner-Doudoroff pathways. It appears to acquire pyruvate, acetyl coenzyme A (acetyl-CoA), and oxaloacetate via degradation of externally derived citrate, malate, and amino acids and may use compound interconversion and oxidoreductases to generate and recycle reductive power. The initial genome assembly was fragmented in an unusual gene that is hypervariable within a repeat region. Such extreme local variation is rare but characteristic of genes that confer traits under pressure to diversify within a population. Notably, the four major repeated 9-mer nucleotide sequences all generate a proline-threonine-aspartic acid (PTD) repeat. The genome of an abundant Colwellia psychrerythraea population has a large extracellular protein that also contains the repeated PTD motif. Although we do not know the host for the BD1-5 cell, the high relative abundance of the C. psychrerythraea population and the shared surface protein repeat may indicate an association between these bacteria.IMPORTANCE CPR bacteria are generally predicted to be symbionts due to their extensive biosynthetic deficits. Although monophyletic, they are not monolithic in terms of their lifestyles. The organism described here appears to have evolved an unusual metabolic platform not reliant on glucose or pentose sugars. Its biology appears to be centered around bacterial host-derived compounds and/or cell detritus. Amino acids likely provide building blocks for nucleic acids, peptidoglycan, and protein synthesis. We resolved an unusual repeat region that would be invisible without genome curation. The nucleotide sequence is apparently under strong diversifying selection, but the amino acid sequence is under stabilizing selection. The amino acid repeat also occurs in a surface protein of a coexisting bacterium, suggesting colocation and possibly interdependence.

Microbial diversity and volatile profile of traditional fermented yak milk

Previous research reported that fermented yak milk had a diverse microbial composition. For this study, raw yak milk, qula, and fermented yak milk samples were collected from the Aba Tibetan autonomous region of China. The genus and species microbial composition of these samples were analyzed by high-throughput sequencing of 16S rRNA and groEL gene amplicons, and the volatile profile of the samples was quantified by gas chromatography-mass spectrometry. The results indicated variation in abundance of microbiota at the genus level among the fermented yak milk samples, with Lactobacillus as the most abundant genus in the majority of samples, ranging from 41.6 to 98.3%. The volatile profile of the samples varied among those collected from different villages. Correlations between bacterial composition and volatile compounds of the samples were also observed. Lactobacillus displayed a significant correlation with volatile compounds such as benzaldehyde, 2,3-pentanedione, ethanol, and ethyl acetate, whereas the samples with relatively high abundance of Streptococcus and Lactococcus displayed relatively low contents of volatile compounds.

Links between microbial compositions and volatile profiles of rice noodle fermentation liquid evaluated by 16S rRNA sequencing and GC-MS

The study investigated the correlations between microbial compositions and volatile profiles of six mixed culture rice noodle fermentation liquid (RNFL) samples labelled by YI, XX, HL, XL, KJ, and JJ, respectively. Through 16S rRNA high-throughput sequencing technology (HTS), the main microbial genera identified in RNFL samples were Lactobacillus, Burkholderia, Gluconacetobacter, Lactococcus, and Leuconostoc (≥5% of operational taxonomic units). A total of one hundred and ten volatile compounds were detected by using SPME/GC-MS. E-nose data showed that HL, XX, and JJ shared similarities in flavor characteristics. Correlation analysis between bacterial genus and volatile compounds indicated that Lactobacillus and Gluconacetobacter were strongly correlated with most flavor compounds detected. Moreover, YI and XX had higher fragrance scores in sensory evaluation, indicating thicker fermented rice fragrance than other RNFL samples.

Effects of different temperatures on bacterial diversity and volatile flavor compounds during the fermentation of suancai, a traditional fermented vegetable food from northeastern China

The bacterial diversity and volatile flavor compounds (VFCs) during suancai fermentation in different temperatures were investigated by Illumina Hiseq sequencing and GC-MS. Firmicutes and Proteobacteria were observed to be the dominant phyla during the fermentation. Lactobacillus, Serratia, Leuconostoc, Pseudomonas, Pseudomonas, Pediococcus, etc., were observed as the main genus. Serratia and Pseudomonas predominated the early stage of suancai fermentation, while Lactobacillus predominated the later stage. Leuconostoc predominated the fermentation at 10 °C and 15 °C, while Weissella and Lactococcus predominated at 20 °C and 25 °C. A total of 86 VFCs were detected in all suancai samples. With the increase of the fermentation temperature, the kinds of VFCs were also increased. Lactobacillus, Pediococcus, Lactococcus, Brochothrix, Psychrobacter, Pseudoalteromonas, Acinetobacter and Enterobacter were the important bacteria related to VFCs during the fermentation. The bacteria were highly correlated with the VFCs in suancai fermentation. As the most dominant genus, Lactobacillus was significantly positive correlated with 13 VFCs. The correlation between the bacteria and VFCs in suancai could be used to search for microbial markers. In conclusion, 20 °C could accelerate the maturation and improve the sensory quality of suancai. This study could provide useful guidelines for screening of strains that contribute to the flavor formation in suancai fermentation.

A trinuclear Co(II) cluster-based metal–organic framework for selective gas sorption and protective effect on acute glomerulonephritis by inhibiting NF-κb pathway

By using a nanosized tetracarboxylate ligand 2,3,5,6-tetrakis(4-carboxyphenyl)pyrazine (H4TCPP) as a building block, the synthesis of a new microporous Co-based metal–organic framework was performed by making Co(NO2)3·6H2O and the presence of bpy ligand to react under solvothermal reaction, and its chemical formula is [Co3(OH)2(H2TCPP)2(bpy)](DMF)3 (1, bpy = 4,4ʹ-bipyridine). Gas adsorption studies reveal that the mixtures of C2H2/CH4 and C2H2/CO2 could be selectively separated by the obtained activated 1a. The protective effect of compound on AGN was further evaluated in vitro. The RT-PCR was carried out to determine the relative expression of tnf-α, nf-κb in glomerular cells after bacterial infection and compound treatment. The IL-1β and IL-18 content in glomerular cells was also evaluated by ELISA after compound treatment. Finally, the results obtained through molecular docking exhibited possible regulation mechanism on regulation of binding affinity between DNA and target protein.

Identification of human skin bacteria attractive to the Asian Tiger mosquito.

Aedes albopictus is a vector of arboviruses and filarial nematodes. Originating from Asia, this mosquito has rapidly expanded its geographical distribution and colonized areas across both temperate and tropical regions. Due to the increase in insecticide resistance, the use of environmentally friendly vector control methods is encouraged worldwide. Using methods based on semiochemicals in baited traps are promising for management of mosquito populations. Interestingly, human skin microbiota was shown to generate volatile compounds that attract the mosquito species Anopheles gambiae and Aedes aegypti. Here, we investigated the composition of skin bacteria from different volunteers and the attractive potential of individual isolates to nulliparous Ae. albopictus females. We showed that three out of 16 tested isolates were more attractive and two were more repulsive. We identified dodecenol as being preferentially produced by attractive isolates and 2-methyl-1-butanol (and to a lesser extent 3-methyl-1-butanol) as being overproduced by these isolates compared with the other ones. Those bacterial volatile organic compounds represent promising candidates but further studies are needed to evaluate their potential application for baited traps improvement.

Bacterial populations and volatile organic compounds associated with meat spoilage

The aim of the study was to detect volatile organic compounds acting as markers of spoilage for raw chilled beef stored under vacuum at 4 °C for 15 days. We also determined the relationship of the volatile compounds with microbial and organoleptic properties associated with shelf life. Volatile organic compounds were analysed by multisensory analysis using an electronic nose sensor. Increasing aldehydes, ketones, and alcohols were measured in beef during the storage period. An increase in volatile chemical compounds during storage was correlated with an increased level of Lactobacillus, the predominant group of microorganisms on the beef at the end of the study. Maximum concentrations of volatile chemical compounds were determined at the end of the shelf life of the stored beef. Lactic acid bacteria were the main microorganisms that caused spoilage and are suitable for predicting the shelf life of raw chilled vacuum packaged beef using the electronic nose device at the threshold of 5.0-6.0 log CFU/g.

Composition and Significance of Bacterial Microbiota and Volatile Organic Compounds of Swiss-Dutch-Type Cheese as Determined by PCR-DGGE and HS-GC

Composition and Significance of Bacterial Microbiota and Volatile Organic Compounds of Swiss-Dutch-Type Cheese as Determined by PCR-DGGE and HS-GC

2-Mercaptobenzimidazole Schiff Bases: Design, Synthesis, Antimicrobial Studies and Anticancer Activity on HCT-116 Cell Line.

Increased rate of mortality due to the development of resistance to currently available antimicrobial and anticancer agents initiated the need to develop new chemical entities for the treatment of microbial infections and cancer. The present study was aimed to synthesize and evaluate antimicrobial and anticancer activities of Schiff bases of 2-mercaptobenzimidazole. The Schiff bases of 2-mercaptobenzimidazole were synthesized from 4-(2-(1H-benzo[d]- imidazol-2-ylthio)acetamido)benzohydrazide. The synthesized compounds were evaluated for antimicrobial and anticancer activities by tube dilution method and Sulforhodamine-B (SRB) assay, respectively. Compounds 8 (MICpa, an = 2.41, 1.20 µM/ml), 10 (MICse, sa = 2.50 µM/ml), 20 (MICec = 2.34 µM/ml) and 25 (MICca = 1.46 µM/ml) showed significant antimicrobial activity against tested bacterial and fungal strains and compounds 20 (IC50 = 8 µg/ml) and 23 (IC50 = 7 µg/ml) exhibited significant anticancer activity. In general, the synthesized derivatives exhibited moderate antimicrobial and anticancer activities. Compounds 8 and 25 having high antifungal potential among the synthesized compounds may be taken as lead molecules for the development of novel antifungal agents.

Bacterial Proteinaceous Compounds With Multiple Activities Toward Cancers and Microbial Infection.

In recent decades, cancer and multidrug resistance have become a worldwide problem, resulting in high morbidity and mortality. Some infectious agents like Streptococcus pneumoniae, Stomatococcus mucilaginous, Staphylococcus spp., E. coli. Klebsiella spp., Pseudomonas aeruginosa, Candida spp., Helicobacter pylori, hepatitis B and C, and human papillomaviruses (HPV) have been associated with the development of cancer. Chemotherapy, radiotherapy and antibiotics are the conventional treatment for cancer and infectious disease. This treatment causes damage in healthy cells and tissues, and usually triggers systemic side-effects, as well as drug resistance. Therefore, the search for new treatments is urgent, in order to improve efficacy and also reduce side-effects. Proteins and peptides originating from bacteria can thus be a promising alternative to conventional treatments used nowadays against cancer and infectious disease. These molecules have demonstrated specific activity against cancer cells and bacterial infection; indeed, proteins and peptides can be considered as future antimicrobial and anticancer drugs. In this context, this review will focus on the desirable characteristics of proteins and peptides from bacterial sources that demonstrated activity against microbial infections and cancer, as well as their efficacy in vitro and in vivo.

Synthesis of novel 3-[(2R*)-2-[(2S*)-6-fluoro-3,4-dihydro-2H-chromen-2-yl]-2-hydroxyethyl]-urea/thiourea derivatives and evaluation of their antimicrobial activities

A new series of biologically active 3-[(2R*)-2-[(2S*)-6-fluoro-3,4-dihydro-2H-chromen-2-yl]-2-hydroxyethyl]-urea/thiourea derivatives (1) have been designed and synthesized in four steps from 6-fluoro-3,4-dihydro-2-(oxiran-2-yl)-2H-chromene (2). The structures of newly synthesized compounds (1a–j) were confirmed by 1H, 13C NMR, and HRMS. The major advantages of the present article include the development of an efficient eluent system for good separation of diastereomers (2a and 2b) with high yields and synthesis of (R*)-2-(benzylamino)-1-((S*)-6-fluoro-3,4-dihydro-2H-chromen-2-yl)ethanol (3) in high yields (87%) from epoxide (2a) through new reaction conditions. The synthesized compounds (1a–j) exhibited moderate to excellent antimicrobial activities against both bacterial strains (gram + Ve and gram –Ve strains) and fungal strains. Among the tested compounds, promising lead compounds were identified (compounds 1a and 1d against bacterial strains and compound 1h and 1j against fungal strains) and their antimicrobial activities are comparable with the reference standard.

Soil bacterial diffusible and volatile organic compounds inhibit Phytophthora capsici and promote plant growth.

Biotic interactions through diffusible and volatile organic compounds (VOCs) are frequent in nature. Soil bacteria are well-known producers of a wide range of volatile compounds (both organic and inorganic) with various biologically relevant activities. Since the last decade, they have been identified as natural biocontrol agents. Volatiles are airborne chemicals, which when released by bacteria, can trigger plant responses such as defence and growth promotion. In this study, we tested whether diffusible and volatile organic compounds (VOCs) produced by soil bacterial isolates exert anti-oomycete and plant growth-promoting effects. We also investigated the effects of inoculation with VOC-producing bacteria on the growth and development of Capsicum annuum and Arabidopsis thaliana seedlings. Our results demonstrate that organic VOCs emitted by bacterial antagonists negatively influence mycelial growth of the soil-borne phytopathogenic oomycete Phytophthora capsici by 35% in vitro. The bacteria showed plant growth promoting effects by stimulating biomass production, primary root growth and root hair development. Additionally, we provide evidence to suggest that these activities were deployed by the emission of either diffusible organic compounds or VOCs. Bacterial VOC profiles were obtained through solid phase microextraction (SPME) and analysis by gas chromatography coupled with mass spectrometry (GC-MS). This elucidated the main volatiles emitted by the isolates, which covered a wide range of aldehydes, alcohols, esters, carboxylic acids, and ketones. Collectively, twenty-five VOCs were identified to be produced by three bacteria; some being species-specific. Our data show that bacterial volatiles inhibits P. capsici in vitro and modulate both plant growth promotion and root system development. These results confirm the significance of soil bacteria and highlights that ways of harnessing them to improve plant growth, and as a biocontrol agent for soil-borne oomycetes through their volatile emissions deserve further investigation.

Determination of bacterial intracellular and extracellular biotransformation compounds and biodegradation of kerosene based industrial rolling oils via gas chromatography-mass spectrometry

In the aluminum and steel industry there is no specialized bioremediation of the pure or spent hydrocarbon rolling oils. Hazardous waste management companies remove the spent oils which eventually end up being dumped at local hazardous material dump sites. The lack of an environmentally friendly strategy to reduce the hazardous waste from factories was incentive for this research. The aim was to determine and monitor an indigenous Achromobacter aegrifaciens bacterial biotransformation/biodegradation of Kerosene based rolling oils including the additives: methyl laurate, lauric acid and Shellsol D100. This was done via dehydrogenase assays and Gas Chromatography-Mass Spectrometry. Achromobacter aegrifaciens bacterial biotransformation was also compared to that of an exogenous consortium of Lysinibacillus fusiformis and Pseudomonas synaxantha. Results were analyzed statistically, using SPSS version 24. The mean differences were significant at the 0.05 level for both DHA and GCMS. Further, subterminal oxidation was determined to be the main activation mechanism for the biotransformation. Methylation occurred during rolling oil biotransformation but was more prevalent in biotransformations of the additives, especially methyl laurate. Methylation resulted in less efficient biotransformations compared to subterminal oxidation. This bioremediation strategy can now be further established for larger volume bioreactors as we established that the toxic monoaromatic compounds were successfully degraded at the end of five weeks making this bioremediation strategy a viable alternative to the current dumping by waste companies.

Cell density-dependent auto-inducible promoters for expression of recombinant proteins in Pseudomonas putida.

SummaryInducible promoters such as Plac are of limited usability for industrial protein production with Pseudomonas putida. We therefore utilized cell density‐dependent auto‐inducible promoters for recombinant gene expression in P. putida KT2440 based on the RoxS/RoxR Quorum Sensing (QS) system of the bacterium. To this end, genetic regions upstream of the RoxS/RoxR‐regulated genes ddcA (PR ox132) and PP_3332 (PR ox306) were inserted into plasmids that mediated the expression of superfolder green fluorescent protein (sfGFP) and surface displayed mCherry, confirming their promoter functionalities. Mutation of the Pribnow box of PR ox306 to the σ70 consensus sequence (PR ox3061) resulted in a more than threefold increase of sfGFP production. All three promoters caused cell density‐dependent expression, starting transcription at optical densities (OD 578) of approximately 1.0 (PR ox132, PR ox306) or 0.7 (PR ox3061) as determined by RT‐qPCR. The QS dependency of PR ox306 was further shown by cultivating P. putida in media that had already been used for cultivation and thus contained bacterial signal molecules. The longer P. putida had grown in these media before, the earlier protein expression in freshly inoculated P. putida appeared with PR ox306. This confirmed previous findings that a bacterial compound accumulates within the culture and induces protein expression.

Identification of volatile organic compounds for the biocontrol of postharvest litchi fruit pathogen Peronophythora litchii

Litchi is an important economic fruit in subtropical countries. The litchi downy blight (LDB) caused by the oomycete Peronophythora litchii severely affects the production and quality of litchi fruit, and is widespread in almost all litchi production regions of China. Therefore, there is an urgent need for effective and sustainable control strategies against LDB. Our previous study showed that Bacillus amyloliquefaciens LI24 and PP19, B. licheniformis HS10, B. pumilus PI26, and Exiguobacterium acetylicum SI17 are promising biocontrol agents (BCAs) in controlling LDB, and their volatile organic compounds (VOCs) could inhibit the growth of P. litchii in vitro. In this study, we found that pre-exposure of litchi fruit to VOCs produced by PP19, SI17 and PI26 can significantly reduce the severity of LDB during 36 h to 72 h post inoculation. We further analyzed VOCs produced from the three BCAs (i.e., PP19, SI17, PI26) by solid phase microextraction gas chromatography-mass spectrometry (SPME-GC–MS), and found that their chemical compositions varied substantially over incubation time and between BCAs. In total, 70, 98, 101 chemicals were detected in PP19, SI17, PI26 from 24 to 72 h of incubation, respectively; 17 of them were commonly produced at more than one time points by PP19, and 11 were selected for further study. Two of the compounds 1-(2-Aminophenyl)ethanone (EA) and Benzothiazole (BTH) showed inhibitory activity against both P. litchii on plates and LDB on litchi fruit when the compounds were directly applied, while another compound α-Farnesene (AF) was able to suppress LDB in vivo, but did not exhibit antagonistic activity against the pathogen in vitro, suggesting that it may act through induction of host defense mechanisms. Our results showed that the bacterial VOCs and compounds of BTH or AF could be promising for the control of LDB on harvested litchi fruit.

Emerging Health Concepts in the Probiotics Field: Streamlining the Definitions.

The concept of traditional probiotics was initially based on the observations of Elie Metchnikoff in 1907. He thus suggested that the regular consumption of fermented dairy products with lactic acid bacteria (LAB), such as yogurt, was associated with enhanced health and longevity in elderly Bulgarian people. Since then, the term probiotic has been always linked to beneficial bacteria for the host health, although its precise definition has evolved over the time (Figure 1A). Nowadays, thanks to the huge increase in the knowledge of the human gut microbiota and the importance of microbiota imbalances (dysbiosis) in several diseases and syndromes, probiotics can be used to restore the normal balance of the intestinal ecosystem as novel health promoting strategy. This new trend highlights the use of commensal bacteria as probiotics is the natural way to restore a healthy situation within different human ecosystems (intestinal, vaginal, skin…) opening the door to a new type of probiotics commonly called either Next-Generation Probiotics (NGPs) or Live Bio-Therapeutic Products (LBPs). Furthermore, the possibility of using non-viable bacteria, bacterial compounds, growth promoting substrates has opened the door to many new preventive therapy and options related to the field. Open in a separate window Figure 1 (A) Timeline of selected items in the history of probiotic related terms; (B) Scheme of the main terms related to probiotic field.

Volatile Compounds of Bacterial Origin: Structure, Biosynthesis, and Biological Activity

Microorganisms produce various volatile compounds, including volatile organic compounds and complex combinations of volatile compounds. The ecological and functional role of these compounds is presently the subject of intense study. Volatile organic compounds of microbial origin may possess antimicrobial properties, suppress or stimulate plant growth, and act as signals for long-distance communication between organisms (infochemicals), which propagate in the air and in aquatic solutions. Chemical diversity of volatile organic compounds of microbial origin provides a source of new compounds which may find application in medicine, biotechnology, and agriculture. Presently known bacterial volatile compounds, their structure, biosynthesis, and biological activity are discussed, with special emphasis on organic volatile compounds and their effect on bacteria.