Archaea in Food Microbiology: Are They Really Possible Threat or Not?

Figure 1: Simplified universal phylogenetic tree showing the evolution of the three major domains from a common ancestral life form [4].

Archaea are newly emerged domain of single-celled organisms that belong to prokaryotes. It was not until 1977 where Carl Woese and George E Fox classified this group of microorganisms separately in phylogenetic tree based on the sequencing of rRNA gene technique and not under bacteria as was thought before [1]. Archaeal microorganisms share some properties between both eukarya and bacteria. For instance, they have circular chromosome like bacteria but translation and transcription process are similar to that of eukarya [2]. However, Archaea domain is more closely related to eukaryota than bacteria as could be illustrated in (Figure 1) [3]. However, Archaea and bacteria are both similar in being free of membrane bound organelles in addition to the lack of true nucleus (membrane-bound nucleus) in contrast to the eukarya [4].

Since Archaea lineage is considered a recent discovery, little is known about it. Archaea are widely distributed in nature from ordinary habitat to harsh environmental conditions. However, many of them are uncultivable in conventional culture media and only molecular techniques could reveal their abundance and diversity in different environments [5]. Accordingly, it could be expected that these organisms may survive tough processing conditions of food and beverage industry and at the same time they may pass undetected using standard culture media in quality control laboratory.

While all efforts and intentions are diverted toward known pathogens that are problematic in the food and the beverage industry (when talking about safety and quality control), yet Archaea lack sufficient attention. So, scientific studies are still deficient in revealing many of mysteries that are related to this domain. This may include but not limited to the following:

Role of Archaea in human pathogenesis

Archaea are known for their ability to colonize and persist in different human parts such as mouth, vagina and colon [6-10]. Nevertheless, there are not any concrete data till now that could point to implication of Archaea to human pathogenesis [11]. However, some researchers have highlighted studies that may show involvement of some Archeal species (e.g. Sulfolobus solfataricus, Methanococcus jannaschii, Archaeoglobus fulgidus, Actinobacillus actinomycetemcomitans, haloarchaea and methanoarchaea) as human pathogen [12,13].

Interaction of Archaea with food and beverages

Although many types of Archaea have found to produce several important organic solutes in biotechnological applications including preservatives [14], yet the biochemical interaction with food and beverage components including the effect of conventionally known preservatives is still anonymous in most cases. This area requires extensive studies as bimolecular interaction of Archaea of chemical entities may be unique from that of other microorganism's viz. bacteria and fungi. An interesting example is the effect of statins on methanogenic Archaeon Methanobrevibacter smithii and inhibits cell membrane biosynthesis [15].

Adequacy of microbiological quality monitoring of Archaea

Till now the conventional microbiological culture media and techniques are widely implemented in microbiology laboratory in microbiological quality control at many industries. Although traditional or culture-based tests are relatively inexpensive and reproducible, they are known to underestimate the total number of bacteria by up to several orders of magnitude, even with prolonged incubation times and temperature variations. It has long been documented that artificial culture media lead to only a very small fraction (0.01-1%) of the total viable microorganism present in any given sample [16]. VBNC cells have also been shown to be antibiotic tolerant, as well as exhibiting tolerance to heavy metals, environment stress conditions and ethanol [17]. Many of Archaea cannot be detected by ordinary culture media but only it could be captured by the new molecular biology techniques such as nucleic- acid-based methods [4].

Potential ability of Archaea to form biofilm

Archaea have the ability to establish biofilm as mechanism for survival. Again little is known till now on the biofilm formation by Archaea [18]. Archaea can form complex biofilm on biotic and abiotic surfaces, in normal and hard conditions and formed from mono species or mixed communities with varies architecture as an adaptive mechanism to the change of the environmental conditions [19]. It is obvious that this survival ability may pose threat for any water processing and distribution system in the manufacturing facility which may impact the final product accordingly.

Survival of Archaea in harsh environmental conditions

Many Archeal species are able to survive extreme environmental and chemical conditions. The survival is largely controlled by the cell cytoplasmic membrane [20]. This may raise question about their ability to withstand many detrimental conditions that are used during food and beverage manufacturing processing steps. An interesting study revealed the survival of Archaea (Euryacheota) along with bacteria in edible commercial salt samples that were able to withstand high salt conditions as extremely halophilic microbes and ingested [21]. Another example includes the ability of survival and gut colonization of methanogenic archaea (M. smithii) from raw and treated milk [22]. Archaea can survive extremes of pH, salinity, temperature, pressure, radiation and many other unfavorable conditions of life [23]. The effect of chemical disinfectants and antiseptics is still questionable.

The human knowledge about microorganisms in domain Archaea is still in its infancy. Accordingly, no definitive roles about its adverse effects on human or consumable food materials have been established till now on solid scientific background. Hence, extensive researches should be conducted on these microorganisms to draw logical conclusion about their impact rather than ignoring them in order to avoid any possible futuristic harm or damage to human health or even life. After the above mentioned obstacles that represent some of the challenges, the industry engines should not just move on and ignore the presence of Archaea in any of our consumable and ingestible products before extensive scientific research could judge their effect and safety on our quality of life.

N/A

None to declare.

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