The C50 carotenoid bacterioruberin regulates membrane fluidity in pink-pigmented Arthrobacter species

Carotenoids have several crucial biological functions and are part of the cold adaptation mechanism of some bacteria. Some pink-pigmented Arthrobacter species produce the rare C50 carotenoid bacterioruberin, whose function in these bacteria is unclear and is found mainly in halophilic archaea. Strains Arthrobacter agilis DSM 20550T and Arthrobacter bussei DSM 109896T show an increased bacterioruberin content if growth temperature is reduced from 30 down to 10 °C. In vivo anisotropy measurements with trimethylammonium-diphenylhexatriene showed increased membrane fluidity and a broadening phase transition with increased bacterioruberin content in the membrane at low-temperature growth. Suppression of bacterioruberin synthesis at 10 °C using sodium chloride confirmed the function of bacterioruberin in modulating membrane fluidity. Increased bacterioruberin content also correlated with increased cell resistance to freeze–thaw stress. These findings confirmed the adaptive function of bacterioruberin for growth at low temperatures for pink-pigmented Arthrobacter species.

Evaluation of the effects of pigments produced by environmental bacteria on cancer cells

Cancers are a collection of incapacitating diseases in which cells initiate to divide and spread to adjacent tissues in an uncontrolled manner. Many researches demonstrated the potential of bacterial pigments as promising anticancer agents Therefore, in this study, the cytotoxic effects of bacterial pigments were evaluated in breast and colon cancer cell lines. In this study, a total of 90 samples were collected from air, water, and soil from 28 different geographical areas of Iran. Forty isolates were selected based on differences in colony color and geographic regions. The MTT assay was used to evaluate the effect of pigment on MCF-7 and SW-48 cells. Bacteria whose pigment had the highest cytotoxic effect on cell lines were selected. Accurate identification was performed using PCR, and their relative purity was measured using TLC. Bacteria isolated from any three ecosystems are capable of producing pigments. Pigment-producing bacteria are more abundant in the soil than air and water. Among pigment-producing bacteria, 3 isolates had the highest cytotoxicity on MCF-7 cells, and 3 isolates had the greatest effect on SW-48 cells. The results of sequencing of isolates at the BLAST site showed that 6 isolates with cytotoxic effects were identified (Micrococcus xinjiangensis, Dietzia, Arthrobacter agilis, Exigubacterium mexicanum, Bacillus beijingensis). Chromatography shows that these pigmented bacteria have different pigment components.Pigment extraction from bacteria can be used as a complementary therapy or other therapies for breast and colon cancer in the future.

Effect of Different Bacterial Strains on the Germination Forage Pea (Pisum sativum ssp. arvense L.) under Salt Stress

Background: Stress factors are one of the elements that affect yield in agricultural production and salinity stress is one of the most important stress factors. Pea is an important source of nutrient for human nutrition, as well as a very important legume plant that used as animal feed. Methods: The experiment, which was set up according to factorial arrangement in random plots, was carried out with 10 replications and a forage pea line was used. Seven different (0, 50, 100, 150, 200, 250 and 300%) salt concentrations and two different bacterial strains (Bacillus sp. and Arthrobacter agilis) were used in the study. In the study, the effects of different bacterial strains on germination percentage (%), germination rate (days), average daily germination (%), peak value (%) and germination value (%) in pea line exposed to salt were investigated. Result: In the study, it was found that bacterial applications in salt stress were statistically significant in all parameters. It was determined that Bacillus sp. strain was more effective for germination percentage and germination rate. 50 mM salt + bacteria applications of the studied genotype and Bacillus sp. and Arthrobacter agilis strains were found to have positive effects on seed germination biology under salt stress.

Arthrobacter bussei sp. nov., a pink-coloured organism isolated from cheese made of cow’s milk

A pink-coloured bacterium (strain KR32T) was isolated from cheese and assigned to the ‘ Arthrobacter agilis group’. Members of the ‘pink Arthrobacter agilis group’ form a stable clade (100 % bootstrap value) and contain the species Arthrobacter agilis , Arthrobacter ruber and Arthrobacter echini , which share ≥99.0 % 16S rRNA gene sequence similarity. Isolate KR32T showed highest 16S rRNA gene sequence similarity (99.9 %) to A. agilis DSM 20550T. Additional multilocus sequence comparison confirmed the assignment of strain KR32T to the clade ‘pink A. agilis group’. Average nucleotide identity and digital DNA–DNA hybridization values between isolate KR32T and A. agilis DSM 20550T were 82.85 and 26.30 %, respectively. The G+C content of the genomic DNA of isolate KR32T was 69.14 mol%. Chemotaxonomic analysis determined anteiso-C15 : 0 as the predominant fatty acid and MK-9(H2) as the predominant menaquinone. Polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol and monoacyldimannosyl-monoacylglycerol. The peptidoglycan type of the isolate was A3α. The carotenoid bacterioruberin was detected as the major pigment. At 10 °C, strain KR32T grew with increased concentrations of bacterioruberin and production of unsaturated fatty acids. Strain KR32T was a Gram-stain-positive, catalase-positive, oxidase-positive and coccus-shaped bacterium with optimal growth at 27–30 °C and pH 8. The results of phylogenetic and phenotypic analyses enabled the differentiation of the isolate from other closely related species of the ‘pink A. agilis group’. Therefore, strain KR32T represents a novel species for which the name Arthrobacter bussei sp. nov. is proposed. The type strain is KR32T (=DSM 109896T=LMG 31480T=NCCB 100733T).

A Mass Spectrometry-Based Study Shows that Volatiles Emitted by Arthrobacter agilis UMCV2 Increase the Content of Brassinosteroids in Medicago truncatula in Response to Iron Deficiency Stress

Iron is an essential plant micronutrient. It is a component of numerous proteins and participates in cell redox reactions; iron deficiency results in a reduction in nutritional quality and crop yields. Volatiles from the rhizobacterium Arthrobacter agilis UMCV2 induce iron acquisition mechanisms in plants. However, it is not known whether microbial volatiles modulate other metabolic plant stress responses to reduce the negative effect of iron deficiency. Mass spectrometry has great potential to analyze metabolite alterations in plants exposed to biotic and abiotic factors. Direct liquid introduction-electrospray-mass spectrometry was used to study the metabolite profile in Medicago truncatula due to iron deficiency, and in response to microbial volatiles. The putatively identified compounds belonged to different classes, including pigments, terpenes, flavonoids, and brassinosteroids, which have been associated with defense responses against abiotic stress. Notably, the levels of these compounds increased in the presence of the rhizobacterium. In particular, the analysis of brassinolide by gas chromatography in tandem with mass spectrometry showed that the phytohormone increased ten times in plants grown under iron-deficient growth conditions and exposed to microbial volatiles. In this mass spectrometry-based study, we provide new evidence on the role of A. agilis UMCV2 in the modulation of certain compounds involved in stress tolerance in M. truncatula.

Whole-Genome Sequences of Two Arthrobacter sp. Strains, 4041 and 4042, Potentially Usable in Agriculture and Environmental Depollution

We report here the draft genome sequences of Arthrobacter sp. strains 4041 and 4042, both of which possibly belong to the diverse Arthrobacter agilis species and are potentially usable as plant biostimulants for agriculture and as depolluting bacteria for the environment.