Taxonomic Diversity and Antimicrobial Potential of Thermophilic Bacteria from Two Extreme Algerian Hot Springs

This study investigated thermophilic bacterial communities from two Algerian hot springs: Hammam Debagh (94–98 °C), recognized as the second hottest spring in the world, and Hammam Bouhadjar (61–72 °C), one of the hottest in northwest Algeria. Thirty isolates were obtained, able to grow between 45 °...

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Main Authors: Marwa Aireche, Mohamed Merzoug, Amaria Ilhem Hammadi, Zohra Yasmine Zater, Keltoum Bendida, Chaimaa Naila Brakna, Meryem Berrazeg, Ahmed Yassine Aireche, Yasmine Saidi, Svetoslav Dimitrov Todorov, Dallel Arabet, Djamal Saidi
Format: Article
Language:English
Published: MDPI AG 2025-06-01
Series:Microorganisms
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Online Access:https://www.mdpi.com/2076-2607/13/6/1425
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author Marwa Aireche
Mohamed Merzoug
Amaria Ilhem Hammadi
Zohra Yasmine Zater
Keltoum Bendida
Chaimaa Naila Brakna
Meryem Berrazeg
Ahmed Yassine Aireche
Yasmine Saidi
Svetoslav Dimitrov Todorov
Dallel Arabet
Djamal Saidi
author_facet Marwa Aireche
Mohamed Merzoug
Amaria Ilhem Hammadi
Zohra Yasmine Zater
Keltoum Bendida
Chaimaa Naila Brakna
Meryem Berrazeg
Ahmed Yassine Aireche
Yasmine Saidi
Svetoslav Dimitrov Todorov
Dallel Arabet
Djamal Saidi
author_sort Marwa Aireche
collection DOAJ
description This study investigated thermophilic bacterial communities from two Algerian hot springs: Hammam Debagh (94–98 °C), recognized as the second hottest spring in the world, and Hammam Bouhadjar (61–72 °C), one of the hottest in northwest Algeria. Thirty isolates were obtained, able to grow between 45 °C and 80 °C, tolerating pH 5.0–12.0 and NaCl concentrations up to 3%. Colonies displayed diverse morphologies, from circular and smooth to star-shaped and Saturn-like forms. All isolates were characterized as Gram-positive, catalase-positive rods or filamentous bacteria. Identification by MALDI-TOF, rep-PCR and 16S rRNA sequencing classified them mainly within <i>Bacillus</i>, <i>Brevibacillus</i>, <i>Aneurinibacillus</i>, <i>Geobacillus</i>, and <i>Aeribacillus</i>, with <i>Geobacillus</i> predominating. Rep-PCR provided higher resolution, revealing intra-species diversity overlooked by MALDI-TOF MS and 16S rRNA. A subset of six isolates, mainly <i>Geobacillus</i> spp., was selected based on phenotypic and genotypic diversity and tested for antimicrobial activity against thermophilic target isolates from the same hot spring environments. Strong inhibition zones (~24 mm) were observed, with <i>Geobacillus thermoleovorans</i> B8 displaying the highest activity. Optimization on Modified Nutrient Agar medium with Gelrite enhanced antimicrobial production and inhibition clarity. These findings highlight the ecological and biotechnological significance of thermophilic bacteria from Algerian geothermal ecosystems. While this study focused on microbial interactions within thermophilic communities, the promising inhibitory profiles reported here provide a foundation for future research targeting foodborne and antibiotic-resistant pathogens, as part of broader efforts in biopreservation and sustainable antimicrobial development.
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spelling doaj-art-30288984ab0c47019c858331e0ca161f2025-08-20T03:27:21ZengMDPI AGMicroorganisms2076-26072025-06-01136142510.3390/microorganisms13061425Taxonomic Diversity and Antimicrobial Potential of Thermophilic Bacteria from Two Extreme Algerian Hot SpringsMarwa Aireche0Mohamed Merzoug1Amaria Ilhem Hammadi2Zohra Yasmine Zater3Keltoum Bendida4Chaimaa Naila Brakna5Meryem Berrazeg6Ahmed Yassine Aireche7Yasmine Saidi8Svetoslav Dimitrov Todorov9Dallel Arabet10Djamal Saidi11Higher School of Biological Sciences of Oran, BP 1042 Saim Mohamed, Cité Emir Abdelkader (EX-INESSMO), Oran 31000, AlgeriaHigher School of Biological Sciences of Oran, BP 1042 Saim Mohamed, Cité Emir Abdelkader (EX-INESSMO), Oran 31000, AlgeriaHigher School of Biological Sciences of Oran, BP 1042 Saim Mohamed, Cité Emir Abdelkader (EX-INESSMO), Oran 31000, AlgeriaLaboratory of Microorganisms Biology and Biotechnology, University of Oran 1 Ahmed Ben Bella, Oran 31000, AlgeriaHigher School of Biological Sciences of Oran, BP 1042 Saim Mohamed, Cité Emir Abdelkader (EX-INESSMO), Oran 31000, AlgeriaHigher School of Biological Sciences of Oran, BP 1042 Saim Mohamed, Cité Emir Abdelkader (EX-INESSMO), Oran 31000, AlgeriaBiotechnology Laboratory for Food and Energy Security, University of Oran 1 Ahmed Ben Bella, Oran 31000, AlgeriaComputer Science Department, University of Abu Bekr Belkaid, Tlemcen 13000, AlgeriaHigher School of Biological Sciences of Oran, BP 1042 Saim Mohamed, Cité Emir Abdelkader (EX-INESSMO), Oran 31000, AlgeriaProBacLab, Laboratório de Microbiologia de Alimentos, Departamento de Alimentos e Nutrição Experimental, Food Research Center, Faculdade de Ciências Farmacêuticas, Universidade de São Paulo, São Paulo 05508-000, SP, BrazilLaboratory of Microbiological Engineering and Applications, Faculty of Natural and Life Sciences, University of Constantine 1, Constantine 25000, AlgeriaHigher School of Biological Sciences of Oran, BP 1042 Saim Mohamed, Cité Emir Abdelkader (EX-INESSMO), Oran 31000, AlgeriaThis study investigated thermophilic bacterial communities from two Algerian hot springs: Hammam Debagh (94–98 °C), recognized as the second hottest spring in the world, and Hammam Bouhadjar (61–72 °C), one of the hottest in northwest Algeria. Thirty isolates were obtained, able to grow between 45 °C and 80 °C, tolerating pH 5.0–12.0 and NaCl concentrations up to 3%. Colonies displayed diverse morphologies, from circular and smooth to star-shaped and Saturn-like forms. All isolates were characterized as Gram-positive, catalase-positive rods or filamentous bacteria. Identification by MALDI-TOF, rep-PCR and 16S rRNA sequencing classified them mainly within <i>Bacillus</i>, <i>Brevibacillus</i>, <i>Aneurinibacillus</i>, <i>Geobacillus</i>, and <i>Aeribacillus</i>, with <i>Geobacillus</i> predominating. Rep-PCR provided higher resolution, revealing intra-species diversity overlooked by MALDI-TOF MS and 16S rRNA. A subset of six isolates, mainly <i>Geobacillus</i> spp., was selected based on phenotypic and genotypic diversity and tested for antimicrobial activity against thermophilic target isolates from the same hot spring environments. Strong inhibition zones (~24 mm) were observed, with <i>Geobacillus thermoleovorans</i> B8 displaying the highest activity. Optimization on Modified Nutrient Agar medium with Gelrite enhanced antimicrobial production and inhibition clarity. These findings highlight the ecological and biotechnological significance of thermophilic bacteria from Algerian geothermal ecosystems. While this study focused on microbial interactions within thermophilic communities, the promising inhibitory profiles reported here provide a foundation for future research targeting foodborne and antibiotic-resistant pathogens, as part of broader efforts in biopreservation and sustainable antimicrobial development.https://www.mdpi.com/2076-2607/13/6/1425thermophilesextreme environmentsMALDI-TOF MSrep-PCR fingerprinting16S rRNAantimicrobial peptides (AMPs)
spellingShingle Marwa Aireche
Mohamed Merzoug
Amaria Ilhem Hammadi
Zohra Yasmine Zater
Keltoum Bendida
Chaimaa Naila Brakna
Meryem Berrazeg
Ahmed Yassine Aireche
Yasmine Saidi
Svetoslav Dimitrov Todorov
Dallel Arabet
Djamal Saidi
Taxonomic Diversity and Antimicrobial Potential of Thermophilic Bacteria from Two Extreme Algerian Hot Springs
Microorganisms
thermophiles
extreme environments
MALDI-TOF MS
rep-PCR fingerprinting
16S rRNA
antimicrobial peptides (AMPs)
title Taxonomic Diversity and Antimicrobial Potential of Thermophilic Bacteria from Two Extreme Algerian Hot Springs
title_full Taxonomic Diversity and Antimicrobial Potential of Thermophilic Bacteria from Two Extreme Algerian Hot Springs
title_fullStr Taxonomic Diversity and Antimicrobial Potential of Thermophilic Bacteria from Two Extreme Algerian Hot Springs
title_full_unstemmed Taxonomic Diversity and Antimicrobial Potential of Thermophilic Bacteria from Two Extreme Algerian Hot Springs
title_short Taxonomic Diversity and Antimicrobial Potential of Thermophilic Bacteria from Two Extreme Algerian Hot Springs
title_sort taxonomic diversity and antimicrobial potential of thermophilic bacteria from two extreme algerian hot springs
topic thermophiles
extreme environments
MALDI-TOF MS
rep-PCR fingerprinting
16S rRNA
antimicrobial peptides (AMPs)
url https://www.mdpi.com/2076-2607/13/6/1425
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