Question

The number of phage on Earth (a) An estimate for the number of phage on Earth can be obtained using data from Bergh et al. \((1989) .\) By taking water samples from lakes and oceans and counting the various phage, one arrives at counts of the order of \(10^{6}=\) \(10^{7}\) phage \(/ \mathrm{mL}\). Using reasonable assumptions about the amount of water on Earth. make an estimate of the number of phage. (b) Work out the mass of all of the phage particles on the Earth using your result from part (a). (Problem suggested by Sherwood Casjens.)

Short answer

The estimated number of phage on Earth is between \(1.332 × 10^{27}\) and \(1.332 × 10^{28}\), and the total mass is between 1332 and 13320 metric tons.

Step-by-step solution

Calculate number of phage

First, we need to understand that the number of phage present in unit volume is given as \(10^6\) to \(10^7\) per mL. The total volume of water on Earth is reportedly approximately 1.332 billion cubic kilometers, which is equivalent to \(1.332 × 10^{21}\) mL. Therefore, to find the total number of phage on Earth, multiply the volume of Earth's water by the number of phage per mL. i.e., \((1.332 × 10^{21} mL) × (10^6 to 10^7 phage/mL) = 1.332 × 10^{27} to 1.332 × 10^{28}\) phage.

Calculate mass of phage

Next, we need to calculate the mass of all phage on Earth. Based on biological data, it is reasonable to assume that the average weight of a phage is about \(10^{-18}\) grams. Therefore, the total mass of all phage on Earth would be the total number of phage times the mass of a single phage i.e., \((1.332 × 10^{27} to 1.332 × 10^{28}) phage × 10^{-18} grams/phage = 1.332 × 10^9 to 1.332 × 10^{10}\) grams. This simplifies to about 1332 to 13320 metric tons of phage on Earth.

Key concepts

Phage Ecology

Phages, or bacteriophages, are viruses that specifically infect bacteria. In the realm of phage ecology, these minuscule entities play a significant role in controlling bacterial populations, thus influencing the nutrient cycles and energy flow within ecosystems.

Understanding phage population dynamics is crucial since they are the most abundant biological entities on the planet. Phage ecology studies the diversity, the distribution of phages in various environments, and their impact on microbial communities. The exercise on estimating phage numbers on Earth is a glimpse into the far-reaching impact these viruses have on global scales.

Researchers engage with questions like how phage diversity affects bacterial evolution and adaptation. The delicate balance maintained between phages and their bacterial hosts is fundamental, as it can influence the outcome of bacterial infections, the decomposition of organic matter, and the overall health of ecosystems. That's why a seemingly simple exercise of estimating the phage population holds much deeper ecological significance.

Biological Oceanography

Biological oceanography investigates the biological aspects of the ocean—its plants, animals, and microbes—and how these are affected by physical, chemical, and geological factors. Phages, as studied in our exercise, form an essential part of marine microbiology—the study of the smallest organisms in the ocean.

In understanding the scope of phage populations, one cannot ignore the immense volume of Earth's oceans, where a multitude of these viruses thrive. As the exercise illustrates, by estimating the concentration of phages per milliliter of seawater, we can infer their staggering abundance in ocean waters. This abundance indicates the significant role of phages in nutrient cycling, especially in the vast and nutrient-poor areas of the open ocean.

The movement of organic matter through marine food webs, including the role of phages in lysing bacteria and thus regenerating nutrients for other organisms, is a core concept of biological oceanography. The exercise indirectly points to the importance of phages in these food webs and the larger biogeochemical cycles of our planet.

Environmental Microbiology

Environmental microbiology is the study of microbial processes in the environment, the diversity of microbial organisms, and their impact on ecological balance. Phages are a critical subject in this field due to their omnipresence and impact on microbial populations and environmental processes.

The approach taken in the textbook exercise, estimating the number of phages, directly relates to understanding Earth's microbiome. Knowing that there are approximately between 1.332 × 10^27 to 1.332 × 10^28 phages on Earth, with a total mass of about 1332 to 13320 metric tons, we grasp the significant biomass and potential influence of these viruses in environmental systems.

Environmental microbiologists study how phages affect bacterial communities by controlling population size and composition, as well as influencing genetic exchange within these populations. The exercise emphasizes the importance of these viral populations: their abundance, distribution, and impact reflect in numerous environmental processes, from nutrient recycling in soils and waters to their potential use in biotechnology and medicine.