Biosurfactants are expected to be a key factor for microbial enhanced oil recovery (MEOR). In this study, we described the novel biosurfactant-producing strain Brevibacillus borstelensis YZ-2 isolated from a low permeability oil reservoir. We purified and characterized the biosurfactants produced by this YZ-2 strain via thin-layer chromatography and MALDI-TOF-MS, revealing them to be fengycins. We additionally used a Box–Behnken design approach to optimize fermentation conditions in order to maximize the biosurfactants production. Core flooding experiments showed that biosurfactants produced by YZ-2 can significantly enhance crude oil recovery. Micro-model tests showed that emulsification and IFT reduction was the main EOR mechanism of the YZ biosurfactant in the oil wet model. In summary, these findings highlight the potential of Brevibacillus borstelensis YZ-2 and its metabolites for MEOR.

The new alkaline/microbe/polymer (AMP) flooding system was first constructed and evaluated for enhancing oil recovery. The system is composed of 0.3 wt% Na₂CO₃, 2 wt% microbial cultures and 0.2 wt% polymer. Compared with the conventional alkaline/surfactant/polymer (ASP) system, the AMP system exhibits identical displacement properties. Chromatography analysis reveals crude oil is not negatively affected by the microbes in AMP system. Further comparative core flooding experiments using the AMP and ASP systems demonstrate that the AMP system possesses greater potential for enhancing heavy oil recovery, which shows the characteristic of two-stage additional oil increment with total additional oil recovery of 17.11%–19.91%.

A novel, moderately thermophilic, Gram-stain-negative bacterium, designated strain J18^T, was isolated from a water-flooded oil reservoir. Cells were aerobic, oxidase- and catalase-positive, with a polar flagellum. Growth occurred at 35–60 °C and at pH 6–8.5. The respiratory quinones were ubiquinone 8 and ubiquinone 9. The dominant cellular fatty acids were C_16 : 0, C_17 : 0cyclo, C_19 : 0cycloω8cand summed feature 8 (C_18 : 1 ω7c/C_18 : 1 ω6c). The polar lipids consisted of phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, phosphatidylcholine, an unidentified aminolipid, an unidentified phospholipid and an unidentified aminophospholipid. The strain showed the highest 16S rRNA gene sequence similarities toTepidiphilus margaritiferDSM 15129^T(98.6 %),Tepidiphilus succinatimandensDSM 15512^T(98.4 %) andTepidiphilus thermophilusDSM 27220^T(98.1 %), respectively, and the similarity to other species was lower than 93 %. In the phylogenetic trees, it constituted a unique sub-cluster within the genusTepidiphilus. The DNA G+C content of strain J18^Twas 64.44 mol%. As compared with the type strains, the genome-to-genome distances of strain J18^Twere 34.7–40 %. These results confirmed the separate species status of J18^Twith its close relatives. On the basis of physiological, chemotaxonomic and phylogenetic analyses along with the low levels of identity at the whole-genome level, it can be concluded that strain J18^Trepresents a new species of the genusTepidiphilus, for which the nameTepidiphilus oleisp. nov. is proposed. The type strain ofT. oleiis J18^T(=CGMCC 1.16800^T=LMG 31400^T).

Tuberculosis (TB) has returned as the leading cause of death caused by a single infectious agent in 2023. Human macrophages and their secreted exosomes play important roles in combating invading Mycobacterium tuberculosis (Mtb). However, a comprehensive understanding of the mechanisms underlying immune regulation in Mtb-infected macrophages, as well as the packaging mechanisms and anti-TB effects of Mtb-treated exosomes, is still lacking. Here, we conducted comprehensive analyses of the macrophages infected with avirulent and virulent Mtb strains (H37Ra and H37Rv) and their exosomes through omics and phenotypic approaches. The results showed that H37Ra stimulated strong immune responses and apoptosis in macrophages to eliminate invading Mtb, while H37Rv induced severe necrosis and immune escape for survival. Interestingly, our results suggest that macrophages kill Mtb in an interferon-gamma (IFN-γ)-independent but compensatory way, highlighting the central role of IFN signaling pathway in anti-TB response. Moreover, we observed selective transport of host and Mtb RNAs from macrophages to exosomes. Notably, H37Ra-treated exosomes displayed a higher anti-TB effect than H37Rv-treated exosomes due to some enriched pro-inflammatory and immune escape-related Mtb proteins in these two exosomes, respectively. In conclusion, our findings shed new light on the immune mechanisms of macrophages in response to Mtb infection, offering a new TB treatment strategy and promising vaccine candidates.