Supplementary Information
Algorithms for estimating thermodynamic properties of biomolecules
Although the thermodynamic properties and revised HKF equation of state parameters
required to calculated values of Gr,i for biomolecules as a function of temperature and pressure
are known for most of the biomolecules listed in Table 1, those for a number of biomolecules
were estimated using the group additivity algorithms taken from Amend and McCollom (2009):
Ξ palmitate  Ξ propanoate  13Ξ(  CH 2  )
(S1)
Ξoleate  Ξ palmitate  2Ξ(  CH 2  )  (Ξoctene  Ξoctane )
(S2)
Ξ palmitoleate  Ξ palmitate  (Ξoctene  Ξoctane )
(S3)
Ξ myristate  Ξ propanoate  11Ξ(  CH 2  )
(S4)
 βhydroxymyristate  Ξ myristate  Ξ hydroxyoctanoate  Ξ octanoate 
(S5)
 glycerol  3 (  CH 2OH  )   (  CH 2  )   (  CH 3 )
(S6)
 heptose   C6 -aldose   C5 -aldose
(S7)
 rhamnose   glucose   hexane   hexanol 
(S8)
 glucosamine   glucose   hexanamine   hexanol 
(S9)
 N-acetylglucosamine   glucose  2 (  CH 2  )   (  CONH2 )   (  CH 2OH)
(S10)
 N-acetylmuramic acid   N-acetylglucosamine   (  COOH)   (  CHCH3 )   (  CH 2  )   (  CH 3 ) (S11)
 diaminopimelic acid   pimelic acid   (  CH 2 NH2 )  2 (  CH 3 )
(S12)
 putrescine  2 (  CH 2  )   (  CH 2 NH2 )
(S13)
 spermidine   putrescine  3 (  CH 2  )   (  CH 2 NH2 )   (  CH 3 )
(S14)
The symbol is used to represent any thermodynamic property or equations of state parameter,
including those for G 0f , H 0f , S0, a1, a2, a3, a4, c1, c2 and . See Table A for values of these
properties and parameters for the indicated biomolecules. The thermodynamic properties and
equation of state parameters for the compounds and groups used in Eq. (S1-S14) were taken
from the following sources: propanoate, hydroxyoctanoate, octanoate and pimelic acid (Shock,
1995); octene and octane (Shock and Helgeson, 1990); glycerol, ΔGr0 at 25oC (Thauer et al.,
1977) and the remaining properties from Eq. (A6); hexane, hexanol, hexanamine, (-CH2OH-), (CH3), (-CH2-), (-CONH2), (-CH2OH), (-COOH), (-CHCH3), (-CH2NH2) (Amend and Helgeson,
1997);C6-aldose, C5-aldose, which correspond to the averages of values C5 and C6 aldoses, and
glucose (Amend and Plyasunov, 2001).
Carbon content and stoichiometries of non-eukaryotic microorganisms
The amount of carbon in microbial cells and the stoichiometry of biomass differ
significantly as a function of several variables such as species type, growth stage, nutrient
limitation and habitat. For instance, in a study that tracked the amount of cell carbon in five
marine and five non-marine microorganisms as a function of starvation time (up to 28 days), it
was found that the most significant factor in the variation of C content was species type, varying
from 10 – 42 fg C cell-1 for marine microbes and 16 – 35 fg C cell-1 for non-marine cells
(Troussellier et al., 1997). On the other end of the size spectrum, bacterioplankton taken from
fresh, estuarine and marine waters from Western Florida have been estimated to contain 112.9 ±
68.9 fg C cell-1 (Kroer, 1994). Similarly, Bratbak (1985) determined that the size range for
Pseudomonas putida NCMB 1960 and natural bacteria from brackish Norwegian estuary waters
(Puddefjorden, Bergen) under various nutrient limitations ranged from 110 – 310 fg C cell-1.
Spanning an even larger range, marine bacterioplankton grown under various C, N, and P
limitations resulted in cells that contained from 3 to 276 fg C cell-1 (Vrede et al., 2002). In the
same study, total cell mass, and the masses of N and P were also determined for marine bacteria
in different growth phases. Exponentially growing cells that were not nutrient limited weighed in
at 429 fg cell-1, with 149 fg of this being carbon (Vrede et al., 2002). Within the experiments
performed on stationary phase bacteria, C-limited experiments had the largest impact on cell
carbon mass, averaging 107 fg cell-1, 39 fg of which was carbon (Vrede et al., 2002). In the deep
biosphere, where organisms are thought to exist under severe energy and nutrient limitations, the
carbon content of microorganisms has been estimated to be between 18 and 86 fg C cell -1
(Whitman et al., 1998, Lipp et al., 2008), but Kallmeyer et al. (2012) estimated a slightly lower
range of 5 to 75 fg C cell-1. Taken together, the amount of carbon estimated to be in noneukaryotic cells varies by at least two orders of magnitude, from 3 to 310 fg C cell-1. Although
the different techniques used to determine the masses of microorganisms could account for some
of the variation in estimated cell sizes, it is unlikely that this accounts for the total range.
Similarly, the chemical formulas that have been used to represent biomass also vary by a
substantial amount depending on numerous factors. One commonly used formula for biomass,
C5H7NO2 (Rittman and McCarty, 2001) (or CH1.4N0.2O0.4) was derived from measuring these
elements in a bacterial mixed culture fed on casein (phosphoproteins) wastewater in the presence
of oxygen (Porges et al., 1956). Organism-specific studies have yielded somewhat different
stoichiometries. For instance, elemental analysis of Nitrospira revealed CH1.9N0.31O0.93
(Blackburne et al., 2007). The hyperthermophiles Thermococcus litoralis and Thermotoga
maritima, grown at their optimal temperatures, have element ratios corresponding to
CH1.7N0.2O0.7S0.006 and CH1.6N0.2O0.6S0.005 (Rinker and Kelly, 2000), similar to thermophilic
fermenters, CH1.8N0.2O0.5 (van Niel et al., 2002). In a large compilation of soil microorganisms,
Cleveland and Liptzin (2007) posit that the microbial ratio of C:N:P is 60:7:1, but their data
show variability based on prevailing vegetation types, and the relationship between C:P is
weaker than that between C:N. Just above the soil, the major elemental abundances for
microorganisms found on leaf litter show more N and P per mole of carbon, C:N:P = 16:4:1 (van
Meeteren et al., 2008).
Marine microorganisms are commonly assumed to have an elemental composition
corresponding to the Redfield ratio, C106H263O110N16P (Redfield et al., 1963), or some revision of
it, e.g., C106H175O42N16P (Anderson, 1995). Although the Redfield ratio has some utility as an
attempt to characterize global bacterioplankton in marine water, it has long been known to be an
over-simplification (Rullkötter, 2006). The content of the major elements in marine planktonic
microorganism varies based on nutrient availability, species, latitude and the prevailing
circulation system (Takahashi et al., 1985, Martiny et al., 2013, Teng et al., 2014, Weber and
Deutsch, 2010). The magnitude of the variation can be substantial. Circulation patterns alone can
cause N:P to vary by at least an order of magnitude (Weber and Deutsch, 2010). Furthermore,
algae and cyanobacteria grown in the laboratory can have N:P from 5:1 to 100:1 depending on
which nutrient is lacking (Geider and La Roche, 2002). However, in their review, Geider and La
Roche (2002) note that C:N is tightly constrained to be about 6.6.
Table S1. Summary of equation of state parameters and the standard molal thermodynamic
properties at 25oC and 1 bar for aqueous biomolecules estimated in this study.
Figure S1. Energy-based biomass yield coefficients, Y, calculated using the positive
contributions to Gsynth (see text), an assumed dry cell mass of 122 fg and Eq. (6). See Table 3
for values of Y in 25oC increments.
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