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Acid-tolerant bacteria such as Streptococcus mutans, Acidobacterium capsulatum, Escherichia coli, and Propionibacterium acidipropionici have developed several survival mechanisms to sustain themselves in various acid stress conditions. Some bacteria survive by minor changes in the environmental pH. In contrast, few others adapt different acid tolerance mechanisms, including amino acid decarboxylase acid resistance systems, mainly glutamate-dependent acid resistance (GDAR) and arginine-dependent acid resistance (ADAR) systems. The cellular mechanisms of acid tolerance include cell membrane alteration in Acidithiobacillus thioxidans, proton elimination by F1–F0–ATPase in Streptococcus pyogenes, biofilm formation in Pseudomonas aeruginosa, cytoplasmic urease activity in Streptococcus mutans, synthesis of the protective cloud of ammonia, and protection or repair of macromolecules in Bacillus caldontenax. Apart from cellular mechanisms, there are several acid-tolerant genes such as gadA, gadB, adiA, adiC, cadA, cadB, cadC, speF, and potE that help the bacteria to tolerate the acidic environment. This acid tolerance behavior provides new and broad prospects for different industrial applications and the bioremediation of environmental pollutants. The development of engineered strains with acid-tolerant genes may improve the efficiency of the transgenic bacteria in the treatment of acidic industrial effluents. Key points: • Bacteria tolerate the acidic stress by methylating unsaturated phospholipid tail • The activity of decarboxylase systems for acid tolerance depends on pH • Genetic manipulation of acid-tolerant genes improves acid tolerance by the bacteria [ABSTRACT FROM AUTHOR]

Estimation of post-mortem time interval (PMI) is a key parameter in the forensic investigation which poses a huge challenge to the medico-legal experts. The succession of microbes within different parts of the human body after death has shown huge potential in the determination of PMI. Human body harbors trillions of microorganisms as commensals. With the death of an individual when biological functions are stopped, these microorganisms behave contrarily along with the invasion of degrading microbes from the environment. Human cadaver becomes a rich source of nutrients due to autolysis of cells, which attracts various invading microorganisms as well as macroorganisms. At different stages of degradation, the succession of microorganisms differs significantly which can be explored for accurate PMI estimation. With the advent of microbial genomics technique and reduction in the cost of DNA sequencing, thanatomicrobiome and epinecrotic community analysis have gained huge attention in PMI estimation. The article summarizes different sources of microorganisms in a human cadaver, their succession pattern, and analytical techniques for application in the field of microbial forensics. Key points: • Thanatomicrobiome and epinecrotic microbiome develop in postmortem human body. • Lack of metabolic, immune, neuroendocrine systems facilitate microbial succession. • Analysis of postmortem microbial communities predicts accurate PMI. [ABSTRACT FROM AUTHOR]

Applications of probiotic bacteria and nanoparticles (NPs) as therapeutic agents have great importance. This study demonstrates a combinatorial approach of both the probiotic Lactobacillus spp. ( Lactobacillus fermentum and Lactobacillus plantarum) with fluorescent cadmium sulfide (CdS) NPs as therapeutic agents to target MCF-7 cancer cells (human breast cancer cells). In this study, facultative anaerobic Lactobacillus was successfully used as a vehicle to transport NPs into MCF-7 cancer cells. The cell viability assay and invasion study along with confocal and field emission scanning electron microscopy (FESEM) confirmed the release of payload (CdS NPs) into cytoplasm without any external stimuli. The biosynthesized CdS NPs of ∼22 nm were characterized by FESEM, transmission electron microscopy (TEM), atomic force microscopy (AFM), and fluorescence spectroscopy. The bacteria-NPs (microbots) interaction was investigated by growth curve studies, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), FESEM, energy dispersive X-ray spectroscopy (EDX), and fluorescence and confocal microscopy. This alternative approach showed an approved and inexpensive delivering mode of specific functional cargos or therapeutic agents into the cancer cells. [ABSTRACT FROM AUTHOR]

Metal pollution is one of the most persistent and complex environmental issues, causing threat to the ecosystem and human health. On exposure to several toxic metals such as arsenic, cadmium, chromium, copper, lead, and mercury, several bacteria has evolved with many metal-resistant genes as a means of their adaptation. These genes can be further exploited for bioremediation of the metal-contaminated environments. Many operon-clustered metal-resistant genes such as cadB, chrA, copAB, pbrA, merA, and NiCoT have been reported in bacterial systems for cadmium, chromium, copper, lead, mercury, and nickel resistance and detoxification, respectively. The field of environmental bioremediation has been ameliorated by exploiting diverse bacterial detoxification genes. Genetic engineering integrated with bioremediation assists in manipulation of bacterial genome which can enhance toxic metal detoxification that is not usually performed by normal bacteria. These techniques include genetic engineering with single genes or operons, pathway construction, and alternations of the sequences of existing genes. However, numerous facets of bacterial novel metal-resistant genes are yet to be explored for application in microbial bioremediation practices. This review describes the role of bacteria and their adaptive mechanisms for toxic metal detoxification and restoration of contaminated sites. [ABSTRACT FROM AUTHOR]

Biofilm-forming and acyl homoserine lactone (AHL) synthase-positive Pseudomonas aeruginosa N6P6 was isolated from seawater after selective enrichment with two polycyclic aromatic hydrocarbons (PAHs), viz. phenanthrene and pyrene. AHL synthesis was detected qualitatively using bioreporter strains. This marine bacterium putatively synthesized N-(3-oxododecanoyl)- l-homoserine lactone and N-butyryl- l-homoserine lactone, which were identified by TLC, GC-MS, and HPLC. Two quorum sensing (QS) genes coding for AHL synthase, i.e., lasI and rhlI, were identified in the bacterium. lasI and rhlI gene expression was studied during biofilm mode of growth at different phases using quantitative real-time PCR (qRT-PCR). The expression of lasI increased with increase in biofilm growth. In contrast, the expression of rhlI decreased during log phase of biofilm growth. The changes in lasI/ rhlI expression level had significant effects ( P < 0.05) on biofilm architecture and subsequent PAH degradation rate. Degradation of phenanthrene and pyrene by P. aeruginosa N6P6 was affected by biofilm growth and lasI expression. The respective phenanthrene degradation for 15, 24, 48, and 72 h old biofilm after 7 days was 21.5, 54.2, 85.6, and 85.7 %. However, the corresponding pyrene degradation was 15, 18.28, 47.56, and 46.48 %, respectively, after 7 days. A significant positive correlation ( P < 0.05) was observed between lasI expression and PAHs degradation. However, in the presence of tannic acid, a QS inhibitor (QSI), PAHs degradation, biofilm formation, and pyocyanin production reduced significantly which confirmed the pivotal role of QS in biodegradation of PAHs. The findings suggest that AHLs play a pivotal role during biofilm development and subsequent bioremediation of PAHs. [ABSTRACT FROM AUTHOR]

Bacteria are widespread in nature as they can adapt to any extreme environmental conditions and perform various physiological activities. Marine environments are one of the most adverse environments owing to their varying nature of temperature, pH, salinity, sea surface temperature, currents, precipitation regimes and wind patterns. Due to the constant variation of environmental conditions, the microorganisms present in that environment are more suitably adapted to the adverse conditions, hence, possessing complex characteristic features of adaptation. Therefore, the bacteria isolated from the marine environments are supposed to be better utilized in bioremediation of heavy metals, hydrocarbon and many other recalcitrant compounds and xenobiotics through biofilm formation and production of extracellular polymeric substances. Many marine bacteria have been reported to have bioremediation potential. The advantage of using marine bacteria for bioremediation in situ is the direct use of organisms in any adverse conditions without any genetic manipulation. This review emphasizes the utilization of marine bacteria in the field of bioremediation and understanding the mechanism behind acquiring the characteristic feature of adaptive responses. [ABSTRACT FROM AUTHOR]

Chemotherapeutic agents have been banned for disease management in aquaculture systems due to the emergence of antibiotic resistance gene and enduring residual effects in the environments. Instead, microbial interventions in sustainable aquaculture have been proposed, and among them, the most popular and practical approach is the use of probiotics. A range of microorganisms have been used so far as probiotics, which include Gram-negative and Gram-positive bacteria, yeast, bacteriophages, and unicellular algae. The results are satisfactory and promising; however, to combat the latest infectious diseases, the search for a new strain for probiotics is essential. Marine actinobacteria were designated as the chemical factory a long time ago, and quite a large number of chemical substances have been isolated to date. The potent actinobacterial genera are Streptomyces; Micromonospora; and a novel, recently described genus, Salinispora. Despite the existence of all the significant features of a good probiont, actinobacteria have been hardly used as probiotics in aquaculture. However, this group of bacteria promises to supply the most potential probiotic strains in the future. [ABSTRACT FROM AUTHOR]