What are the (correct) terms for these flagella-arrangements?

Question

I came across the following diagrams depicting two kinds of arrangement of flagella over cells.

Now according to my (very unreliable) school textbook, the arrangements are termed as:

• A - Cephalotrichous (tuft of flagella on one end)

• B - Lophotrichous (tufts of flagella on both ends)

Whereas another (equally unreliable) book states the exact opposite:

• A - Lophotrichous (tuft of flagella on one end)

• B - Cephalotrichous (tufts of flagella on both ends)

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A spot of cursory Googling reflects this sort of confusion online (compare the images and their labels here) as well.

According to Wikipedia that arrangement A is lophotrichous, but it makes no reference to arrangement B though.

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I tried to figure it out, going by the smattering of Greek I picked up as a Bio. student ( Cephalos = Something to do with the head ; Lophos = something to do with a peak/protuberance ), I arrived at:

Hmm... so cephalotrichous probably means you find the tuft on one "end" (so arrangement A), and ipso facto lophotrichous is arrangement B.

But I guess, I ended up putting a little too much thought into it...

Cephalotrichous is probably used to indicate you have a tuft on the "head" in addition to another tuft on the "tail" (so arrangement B), and ipso facto lophotrichous is arrangement A.

_{At this stage I'm not sure what's more serious: my inability to find an authoritative answer to my question... or my tendency to overthink stuff}

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I'm in a fix.

Could someone clarify, citing (multiple, if possible) authoritative sources, on the distinction between a "cephalotrichous" and a "lophotrichous" arrangement?

Answer 1

A good source on this subject is Tortora's Microbiology. Unfortunately, it uses a different terminology.

Have a look at this image (click on it for a bigger size), chapter 4, page 81:

As you can see, the lophotrichous arrangement is the one with the flagella at one end of the bacterium (which agrees with the arrangement at the Wikipedia page).

However, the opposite arrangement (flagella at both ends) is called amphitrichous (which, by the way, makes more sense), not cephalotrichous.

The text below that image says:

Lophotrichous: a tuft of flagella coming from one pole;

Amphitrichous: flagella at both poles of the cell;

If you assume that "amphitrichous" is synonym of "cephalotrichous", then the correct book would be your second one, which says:

A - Lophotrichous (tuft of flagella on one end)

B - Cephalotrichous (tufts of flagella on both ends)

However, there is no evidence that one should consider "amphitrichous" and "cephalotrichous" as synonyms. Besides that, things seem to be way more complicated: if you search those terms at Google Books, you'll see that most books say that amphitrichous bacteria have only two flagella, one at each end. And, indeed, some have completely opposite definitions.

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Source: Tortora, G., Funke, B. and Case, C. (2010). Microbiology. San Francisco, California: Pearson Benjamin Cummings.

Answer 2

Amphi- Gr. ἀµϕι- on both sides.

Cephalo- Gr. κεϕαλή head.

Lopho- Gr. λόϕος crest (a tuft of . . . upon a head).

In the context of bacterial flagella, cephalotrichous and lophotrichous are synonyms for they both denote a bacterium with a tuft of flagella on one end only, conventiently called "head" (for things tend to have one head, not two, and, with some imagination, bacteria with a tuft of flagella on one end only do look like hairy heads, don't they?); the latter term, i.e., lophotrichous, is more commonly used.