For American pronunciation, both the Oxford dictionary's American pronunciation and the American Heritage dictionary's leave out the /ə/ in words like little, riddle, mantle, metal that I think of as ending /təl/ and /dəl/, but not words ending in other consonants followed by /əl/, like /nəl/, /bəl/, /kəl/. Merriam-Webster uses /təl/, /dəl/ and /nəl/, but uses /əl/ after other consonants; the /əl/ symbolizes the same pronunciation as in Oxford and American Heritage: the /l/ is the nucleus of its own syllable, which contains no vowel.
For British pronunciation, the Cambridge Advanced Learner's Dictionary on-line uses either /l/ and /əl/ for all these words; I think it depends only on the spelling. I believe these are supposed to symbolize the same sound (no schwa). The online global Oxford dictionary seems to use /(ə)l/ for all of these words, meaning the schwa is optional. So presumably the schwa is supposedly left out in RP.
Going to forvo.com and listening to the pronunciation of words, it seems that Americans generally (not always) do put the schwa in after consonants other than /t/ and /d/, but many (not all) Americans leave the schwa out after /t/ and /d/. I'm not a linguist, so I can't say for sure, but I believe these variations are allophonic, meaning that English speakers will perceive them as having the same phoneme. If you leave out the schwa after /t/ or /d/, it is likely you are unaware you're doing so. Don't worry about pronouncing this "right"; you should be understood just as well either way. Even if you're trying to lose a foreign accent, judging from the pronunciations on Forvo, the variation in both native British and native American speakers is large enough that I don't think anybody will notice this. For example, I leave out the schwa after /k/ and /g/, but put it in after /n/.
In my comment above, I said there were no minimal pairs for /əl/ and syllabic /l/, because they are allophonic, but I think I was wrong. The way I speak, there are several multi-word minimal pairs; for example, metal ion versus met a lion, or mental aberration versus meant elaboration.
The answer is all of the above, any of the above, or none of the above. There is no single set of rules for the pronunciation of taxa, and no single interpretation of such rules as some have attempted to compile. As Michael G. Simpson notes under "Pronunciation of Names" in Plant Systematics (2006),
Although scientific names are universal, their pronunciations may vary from region to region, especially between different countries. For example, European pronunciations are often different from those of most American botanists. There are no firm rules as to how scientific names should be pronounced. Very often, pronunciations are influenced by one's native language. One should be flexible and adaptive with regard to pronunciations, as the overriding goal is communications.
Broadly, most English-speaking practitioners of science, medicine, law, architecture, and other disciplines follow traditional English pronunciation of Latin for the Latin and quasi-Latin terms in their fields. There are those who push for what is known as Reformed Academic Pronunciation, a system devised in the late 19th century which is supposed to be closer to the classical pronunciation, and which is closer to the way the words would be pronounced in most continental European languages. William Stearn favors the latter in his widely cited Botanical Latin (1983), but as countless papers, guides, and appendices note:
- Professionals not only use different pronunciations from one place to another, but do not consistently follow the same system themselves.
- People tend to pronounce names based on how they first hear them, as opposed to a particular system of pronunciation
- English speakers don't agree on how to pronounce English; how would they agree on how to pronounce any other language or pseudo-language? (Yes, I am one of those people who is always going on about bruschetta— it's Italian, not French or German.)
Zoologists and bacteriologists moved away from requiring a classical basis for names some time ago, and botanists have moved in the same direction, so perhaps there will be less debate in the future.
Best Answer
The usual English way to pronounce eu in a word from Latin is as "long u" (which in IPA can be any of /juː/, /uː/, /jɜː/, /ɜː/, /jʊ/, /ʊ/, /jə/, /ə/ depending on the context). For example, the first syllable of the word neuter is pronounced the same as the word new—as /njuː/, or /nuː/ in American English. But because Pasteurii is built on a non-Latin name, it is likely to be pronounced with the "nurse" vowel (IPA /ɜː/) instead, which loosely approximates the value of French /œ/. Compare the word Pasteurian/pasteurian, which Merriam-Webster says is pronounced "\ paˈstərēən \" = IPA /pæˈstɜːriən/.
The traditional pronunciation of word-final -ii in a word from Latin is /iaɪ/, but nowadays some people say /ii/ due to influence from the "restored" pronunciation of Latin.
Sarcina should be pronounced with stress on the third-to-last syllable, because the i was short in Latin according to Lewis and Short. If the i were long in Latin, the regular pronunciation in English would put the stress on the second-to-last syllable and give the i the quality of /aɪ/ (as in the word vagina or the place name Carolina). A word ending in -ina that is properly stressed the same way as sarcina is machina in the phrase deus ex machina (the OED indicates stress on the first syllable of machina).
Altogether, I would pronounce Sporosarcina pasteurii as /ˌspɔːroʊˈsɑːrsɪnə pæˈstɜːriaɪ/. The vowel in the second syllable of Sporosarcina could be reduced to /ə/, and in British English, the first syllable might be pronounced with /ɒr/ instead of /ɔːr/. The second syllable of pasteurii might perhaps be pronounced with the "CURE" vowel, as /pæˈstjʊər-/ (or in American English /pæˈstʊr-/ or /pæsˈtʃʊr-/). The last two syllables of pasteurii might be pronounced as /ii/ instead of as /iaɪ/. Of course, in a British English accent, there would be no r consonant after the a in Sporosarcina (/ˌspɔːrəʊˈsɑːsɪnə/ or /ˌspɒrəʊˈsɑːsɪnə/) and in an American English accent this syllable would be pronounced with an r-colored vowel (something like /ˌspɔ˞roʊˈsɑ˞sɪnə/ or /ˌspo˞roʊˈsɑ˞sɪnə/).