Plastic pollution is a worldwide concern causing the death of animals (mainly aquatic fauna) and environmental deterioration. Plastic recycling is, in most cases, difficult or even impossible. For this reason, new research lines are emerging to identify highly biodegradable bioplastics or plastic formulations that are more environmentally friendly than current ones. In this context, microbes, capable of synthesizing bioplastics, were revealed to be good models to design strategies in which microorganisms can be used as cell factories. Recently, special interest has been paid to haloarchaea due to the capability of some species to produce significant concentrations of polyhydroxyalkanoate (PHA), polyhydroxybutyrate (PHB), and polyhydroxyvalerate (PHV) when growing under a specific nutritional status. The growth of those microorganisms at the pilot or industrial scale offers several advantages compared to that of other microbes that are bioplastic producers. This review summarizes the state of the art of bioplastic production and the most recent findings regarding the production of bioplastics by halophilic microorganisms with special emphasis on haloarchaea. Some protocols to produce/analyze bioplastics are highlighted here to shed light on the potential use of haloarchaea at the industrial scale to produce valuable products, thus minimizing environmental pollution by plastics made from petroleum.

This work aims to characterize the haloarchaeal diversity of unexplored environmental salty samples from a hypersaline environment on the southern coast of Jeddah, Saudi Arabia, looking for new isolates able to produce polyhydroxyalkanoates (PHAs). Thus, the list of PHA producers has been extended by describing two species of Halolamina; Halolamina sediminis sp. strain NRS_35 and unclassified Halolamina sp. strain NRS_38. The growth and PHA-production were investigated in the presence of different carbon sources, (glucose, sucrose, starch, carboxymethyl cellulose (CMC), and glycerol), pH values, (5–9), temperature ranges (4–65 °C), and NaCl concentrations (100–350 g L⁻¹). Fourier-transform infra-red analysis (FT-IR) and Liquid chromatography–mass spectrometry (LC-MS) were used for qualitative identification of the biopolymer. The highest yield of PHB was 33.4% and 27.29% by NRS_35 and NRS_38, respectively, using starch as a carbon source at 37 °C, pH 7, and 25% NaCl (w/v). The FT-IR pattern indicated sharp peaks formed around 1628.98 and 1629.28 cm⁻¹, which confirmed the presence of the carbonyl group (C=O) on amides and related to proteins, which is typical of PHB. LC-MS/MS analysis displayed peaks at retention times of 5.2, 7.3, and 8.1. This peak range indicates the occurrence of PHB and its synthetic products: Acetoacetyl-CoA and PHB synthase (PhaC). In summary, the two newly isolated Halolamina species showed a high capacity to produce PHB using different sources of carbon. Further research using other low-cost feedstocks is needed to improve both the quality and quantity of PHB production. With these results, the use of haloarchaea as cell factories to produce PHAs is reinforced, and light is shed on the global concern about replacing plastics with biodegradable polymers.

Calotropis procera (C. procera) is a wild shrub that is a medicinal plant found in abundance throughout Saudi Arabia. In this study, we investigated the phytochemical composition and antigenotoxic properties of the ethanolic extract of C. procera, in addition to the antimicrobial activity of the plant and its rhizospheric actinobacteria effects against pathogenic microorganisms. Soil-extract medium supplemented with glycerol as a carbon source and starch–casein agar medium was used for isolation of actinobacteria from rhizosphere. From the plant, a total of 31 compounds were identified using gas chromatography/mass spectrometry (GC–MS). The main components were α-amyrin (39.36%), lupeol acetate (17.94%), phytol (13.32%), hexadecanoic acid (5.55%), stigmasterol (3.16%), linolenic acid (3.04%), and gombasterol A (2.14%). C. procera plant extract’s antimicrobial activity was investigated using an agar well-diffusion assay and minimum inhibitory concentration (MIC) against six pathogenic microbial strains. The plant extract of C. procera was considered significantly active against Staphylococcus aureus, Klebsiella pneumonia, and Escherichia coli, with inhibition zones of 18.66 mm, 21.26 mm, and 21.93 mm, respectively. The plant extract was considered to be a moderate inhibitor against Bacillus subtilis, with MIC ranging from 0.60–1.50 mg/mL. On the other hand, the isolated actinobacteria were considered to be a moderate inhibitor against S. aureus (MIC of 86 µg/mL), and a potent inhibitor, strain CALT_2, against Candida albicans (MIC of 35 µg/mL). The 16S rRNA gene sequence analysis showed that the potential strains belonged to the genus Streptomyces. The effect of C. procera extract against cyclophosphamide (CP)-induced genotoxicity was examined by evaluating chromosome abnormalities in mouse somatic cells and DNA fragmentation assays. The current study revealed that oral pretreatment of C. procera (50, 100, and 200 mg/kg b.w.) for 1, 7, and 14 days to cyclophosphamide-treated animals significantly reduced chromosomal abnormalities as well as DNA fragmentation in a dose-dependent manner. Moreover, C. procera extract had antimicrobial and antigenotoxic effects against CP-induced genotoxicity.

Breast cancer is the most harmful malignancy in women worldwide. Therefore, in the current study, we investigated the combinatory effect of natural bioactive compounds, including curcumin (Cur) and thymoquinone (TQ), on MCF7 and MDA-MB-231 breast cancer cell lines’ progression. We investigated the Fa values and combination index of Cur and TQ in this context. Moreover, cytotoxicity percentages, annexin-V, proliferation, colony formation, and migration assays were used along with cell cycle analysis. In addition, caspase-3, phosphatidylinositol 3-kinase (PI3K), and protein kinase B (AKT) protein levels were determined by ELISA assessment. The results showed that Cur, TQ, and Cur + TQ induced apoptosis with cell cycle arrest and decreased cell proliferation, colony formation, and migration activities. Cur + TQ combination significantly increased caspase-3 and decreased PI3K and AKT protein levels. These results suggest the promising anticancer benefit of the Cur and TQ combination against breast cancer.

Dental caries is an infectious oral disease caused by the presence of different bacteria in biofilms. Multidrug resistance (MDR) is a major challenge of dental caries treatment. Swabs were taken from 65 patients with dental caries in Makkah, Saudi Arabia. Swabs were cultivated on mitis salivarius agar and de Man, Rogosa, and Sharpe (MRS) agar. VITEK 2 was used for the identification of isolated bacteria. Antibiotic susceptibility testing of the isolated bacteria was performed using commercial antibiotic disks. Ulva lactuca was used as a reducing agent and cellulose source to create nanocellulose and Ag/cellulose nanocomposites. Fourier-transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction spectroscopy (XRD) were used to characterize nanocellulose and Ag/cellulose nanocomposites. The results showed that most bacterial isolates were Streptococcus spp., followed by Staphylococcus spp. on mitis salivarius media. Lactobacillus spp. and Corynebacterium group f-1 were the bacterial isolates on de Man, Rogosa, and Sharpe (MRS) media. The antibiotic susceptibility test revealed resistance rates of 77%, 93%, 0, 83%, 79%, and 79% against penicillin G, Augmentin, metronidazole, ampicillin, ciprofloxacin, and cotrimoxazole, respectively. Ag/cellulose nanocomposites and Ag/cellulose nanocomposites with fluoride were the most effective antibacterial agents. The aim of this work was to assess the antibacterial activity of Ag/cellulose nanocomposites with and without fluoride against bacteria isolated from the oral cavities of patients with dental caries. This study demonstrated that Ag/cellulose nanocomposites have antibacterial properties against multidrug-resistant bacteria that cause dental caries.