Patescibacteria are recently discovered microorganisms, often called “microbial dark matter” due to their elusive nature. These bacteria have unusual characteristics that set them apart from other microbial life. Their unique features and lifestyles have led to increased interest in their widespread presence and influence on diverse ecosystems. This group challenges traditional views of bacterial life, prompting new avenues of exploration in microbiology.
Unveiling Patescibacteria
Patescibacteria are classified within the Candidate Phyla Radiation (CPR), a vast, uncultivated lineage representing a significant portion of microbial diversity. They are characterized by their small cell size and reduced genomes. These genomes often lack genes essential for basic cellular functions, including energy and carbon utilization, and even some for DNA replication and translation.
Due to this genomic reduction, Patescibacteria commonly rely on other organisms for their survival, often forming symbiotic or parasitic relationships. They are known to grow as obligate epibionts, attaching to the surface of host bacteria to acquire necessary metabolic building blocks. Their discovery was not through traditional laboratory cultivation methods, which prove difficult due to their dependence on host organisms, but rather through advanced genomic techniques like metagenomics.
Their Hidden Worlds
Patescibacteria are ubiquitous, found in diverse environments. They thrive in aquatic settings like groundwater, fresh water, and marine habitats, and also inhabit terrestrial environments such as soil and sediments.
They are also associated with animals, including humans, detected in the oral cavity and gut. Despite their small size, Patescibacteria can be abundant in many ecosystems, sometimes accounting for over 10% of the total bacterial community, and even as much as 31% in groundwater. This highlights their pervasive presence in Earth’s microbial communities.
Beyond the Basics: Their Role in Ecosystems and Health
Patescibacteria play roles in microbial ecosystems, primarily through their interactions with host organisms. As symbionts or parasites, they influence the metabolism and survival of their bacterial hosts by acquiring essential metabolic compounds. While their own metabolic capabilities are reduced, they can contribute to biogeochemical cycles by complementing the metabolic activities of their hosts, for instance, through partial pathways for denitrification or hydrogen production.
Emerging research also suggests a potential relevance to human health. Certain Patescibacteria have been linked to specific health conditions or are present in the human microbiome, particularly in the oral cavity. Understanding these interactions could provide insights into microbial community dynamics within the human body and their broader implications for health. Their presence in activated sludge, a component of wastewater treatment, also indicates their involvement in industrial processes.
The Challenge of Understanding Them
Scientists face challenges in fully understanding Patescibacteria, primarily due to their uncultivated nature. Most members cannot be grown in a laboratory using standard methods, making traditional experimental studies difficult. This limitation necessitates a strong reliance on advanced molecular techniques.
Researchers employ metagenomics and single-cell genomics to piece together their complete genetic information directly from environmental samples. Bioinformatics tools are then used to analyze these genomic data, helping scientists infer their metabolic potential and lifestyles. Despite breakthroughs in cultivation for a few species, much about Patescibacteria remains unknown.