High prevalence of antibiotic-resistant and metal-tolerant cultivable bacteria in remote glacier environment

• Published in: Environmental research 2023-12, Vol.239, p.117444-117444, Article 117444
• Main Authors: Sajjad, Wasim, Ali, Barkat, Niu, Hewen, Ilahi, Nikhat, Rafiq, Muhammad, Bahadur, Ali, Banerjee, Abhishek, Kang, Shichang
• Format: Article
• Language: English
• Subjects: Antibiotic resistant genes; Antibiotic-resistant bacteria; Baishui glacier; Metals tolerance genes; Remote glacier environment
• ISSN: 0013-9351; 1096-0953
• DOI: 10.1016/j.envres.2023.117444

Studies of antibiotic-resistant bacteria (ARB) have mainly originated from anthropic-influenced environments, with limited information from pristine environments. Remote cold environments are major reservoirs of ARB and have been determined in polar regions; however, their abundance in non-polar cold habitats is underexplored. This study evaluated antibiotics and metals resistance profiles, prevalence of antibiotic resistance genes (ARGs) and metals tolerance genes (MTGs) in 38 ARB isolated from the glacier debris and meltwater from Baishui Glacier No 1, China. Molecular identification displayed Proteobacteria (39.3%) predominant in debris, while meltwater was dominated by Actinobacteria (30%) and Proteobacteria (30%). Bacterial isolates exhibited multiple antibiotic resistance index values > 0.2. Gram-negative bacteria displayed higher resistance to antibiotics and metals than Gram-positive. PCR amplification exhibited distinct ARGs in bacteria dominated by β-lactam genes blaCTX-M (21.1–71.1%), blaACC (21.1–60.5%), tetracycline-resistant gene tetA (21.1–60.5%), and sulfonamide-resistant gene sulI (18.4–52.6%). Moreover, different MTGs were reported in bacterial isolates, including mercury-resistant merA (21.1–63.2%), copper-resistant copB (18.4–57.9%), chromium-resistant chrA (15.8–44.7%) and arsenic-resistant arsB (10.5–44.7%). This highlights the co-selection and co-occurrence of MTGs and ARGs in remote glacier environments. Different bacteria shared same ARGs, signifying horizontal gene transfer between species. Strong positive correlation among ARGs and MTGs was reported. Metals tolerance range exhibited that Gram-negative and Gram-positive bacteria clustered distinctly. Gram-negative bacteria were significantly tolerant to metals. Amino acid sequences of blaACC,blaCTX-M,blaSHV,blaampC,qnrA, sulI, tetA and blaTEM revealed variations. This study presents promising ARB, harboring ARGs with variations in amino acid sequences, highlighting the need to assess the transcriptome study of glacier bacteria conferring ARGs and MTGs. [Display omitted] •Evaluated antibiotics and metals resistance profiles of cultivable bacteria isolated from glacier environment.•Prevalence of ARGs and MTGs were assessed and bacterial isolates exhibited multiple antibiotics resistance index.•Highlights the co-occurrence and co-selection of MTGs and ARGs in remote glacier environments.•Different bacteria shared the same ARGs, signifying horizontal gene transfer between species.