Disentangling the distinct mechanisms shaping the subsurface oil reservoir bacterial and archaeal communities across northern China

Comprehensive understanding of the aging and biodegradation of polystyrene-based plastics

The extensive utilization and inadequate handling of plastics have resulted in severe environmental ramifications. In particular, plastics composed solely of a carbon-carbon (C-C) backbone exhibit limited degradation due to the absence of hydrolyzable functional groups. Plastics with enduring longevity in the natural environment are susceptible to environmental factors and their intrinsic properties, subsequently undergoing a series of aging processes that culminate in biodegradation. This article focuses on polystyrene (PS), which constitutes 20% of total plastic waste, as a case study. Initially, the application of PS in life and the impacts it poses are introduced. Following that, the key factors influencing the aging of PS are discussed, primarily encompassing its properties (e.g., surface characteristics, additives) and environmental factors (e.g., water matrices, biofilms). Lastly, an overview of microbial degradation of PS is provided, including potential microorganisms involved in PS degradation (bacteria, fungi, algae, and insects), four processes of microbial degradation (colonization, bio-fragmentation, assimilation, and mineralization), and potential mechanisms of microbial degradation. This study provides a comprehensive understanding of the multifaceted influences affecting the aging and biodegradation mechanisms of PS, thereby contributing valuable insights for the future management of plastic pollution.

Horizontal and Vertical Comparison of Microbial Community Structures in a Low Permeability Reservoir at the Local Scale

Petroleum microorganisms play a crucial role in the application of microbial-enhanced oil recovery, and the community structures of petroleum microorganisms have been widely studied. Due to variations in reservoir geological conditions, reservoir microbial communities exhibit unique characteristics. However, previous studies have primarily focused on microbial community changes within a single well, a single block, and before and after water flooding, and thus, cross-horizon and cross-regional comparative studies of in situ microbial communities are lacking. In this study, the 16S rRNA full-length sequencing method was adopted to study bacterial communities in crude oil samples taken from two wells at the same depths (depths of 2425 m and 2412 m) but approximately 20 km apart in the Hujianshan oilfield, located in the Ordos Basin. At the same time, the results were combined with another layer of research data from another article (from a depth of 2140 m). The aim was to compare the differences in the microbial community structures between the oil wells on a horizontal scale and a vertical scale. The results revealed that there were minimal differences in the microbial community structures that were influenced by the horizontal distances within a small range (<20 km), while differences were observed at a larger spatial scale. However, the dominant bacteria (Proteobacteria and Bacteroidetes) in the different oilfields were similar. Vertical depth variations (>300 m) had significant impacts on the communities, and this was mainly controlled by temperature. The greater the depth, the higher formation temperature, leading to an increase in thermophilic and anaerobic bacteria within a community.

pH and Nitrate Drive Bacterial Diversity in Oil Reservoirs at a Localized Geographic Scale

Oil reservoirs are one of the most important deep subsurface biospheres. They are inhabited by diverse microorganisms including bacteria and archaea with diverse metabolic activities. Although recent studies have investigated the microbial communities in oil reservoirs at large geographic scales, it is still not clear how the microbial communities assemble, as the variation in the environment may be confounded with geographic distance. In this work, the microbial communities in oil reservoirs from the same oil field were identified at a localized geographic scale. We found that although the injected water contained diverse exogenous microorganisms, this had little effect on the microbial composition of the produced water. The Neutral Community Model analysis showed that both bacterial and archaeal communities are dispersal limited even at a localized scale. Further analysis showed that both pH and nitrate concentrations drive the assembly of bacterial communities, of which nitrate negatively correlated with bacterial alpha diversity and pH differences positively correlated with the dissimilarity of bacterial communities. In contrast, the physiochemical parameters had little effect on archaeal communities at the localized scale. Our results suggest that the assembly of microbial communities in oil reservoirs is scale- and taxonomy-dependent. Our work provides a comprehensive analysis of microbial communities in oil reservoirs at a localized geographic scale, which improves the understanding of the assembly of the microbial communities in oil reservoirs.

Metagenomic Analysis of Biocide-Treated Neotropical Oil Reservoir Water Unveils Microdiversity of Thermophile Tepidiphilus

Microorganisms are capable of colonizing extreme environments like deep biosphere and oil reservoirs. The prokaryotes diversity in exploited oil reservoirs is composed of indigenous microbial communities and artificially introduced microbes. In the present work, high throughput sequencing techniques were applied to analyze the microbial community from the injected and produced water in a neotropical hyper-thermophile oil reservoir located in the Orinoquia region of Colombia, South America. Tepidiphilus is the dominant bacteria found in both injection and produced waters. The produced water has a higher microbial richness and exhibits a Tepidiphilus microdiversity. The reservoir injected water is recycled and treated with the biocides glutaraldehyde and tetrakis-hydroxymethyl-phosphonium sulfate (THPS) to reduce microbial load. This process reduces microbial richness and selects a single Tepidiphilus genome (T. sp. UDEAICP_D1) as the dominant isolate. Thermus and Hydrogenobacter were subdominants in both water systems. Phylogenomic analysis of the injection water dominant Tepidiphilus positioned it as an independent branch outside T. succinatimandens and T. thermophilus lineage. Comparative analysis of the Tepidiphilus genomes revealed several genes that might be related to the biocide-resistant phenotype and the tolerance to the stress conditions imposed inside the oil well, like RND efflux pumps and type II toxin-antitoxin systems. Comparing the abundance of Tepidiphilus protein-coding genes in both water systems shows that the biocide selected Tepidiphilus sp. UDEAICP_D1 genome has enriched genes annotated as ABC-2 type transporter, ABC transporter, Methionine biosynthesis protein MetW, Glycosyltransferases, and two-component system NarL.