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討論
Winkler技術(shù)是估算浮游生物系統中細菌呼吸最常用的技術(shù)。該技術(shù)具有較高的靈敏度（見(jiàn)表2），但其缺點(diǎn)是無(wú)法隨時(shí)間連續監測氧氣濃度。呼吸通常根據初始和最終氧氣濃度之間的差異計算，假設在孵化期間氧氣呈線(xiàn)性減少。先前的研究已經(jīng)表明，長(cháng)期培養過(guò)程中氧氣的減少并不總是線(xiàn)性的，但可以表現出不同的模式，如指數衰減或指數增加（Biddanda et al.1994；Pomeroy et al.1994）。此外，盡管靈敏度很高，但通常需要較長(cháng)的孵育時(shí)間來(lái)檢測顯著(zhù)的呼吸速率，特別是在低營(yíng)養水域中，在那里孵育可長(cháng)達36小時(shí)。這些長(cháng)時(shí)間孵化的主要后果有充分的記錄；這包括細菌數量和活性的變化（見(jiàn)del Giorgio和Cole 1998年的綜述），以及群落組成的變化（Massana等人，2001年；Gattuso等人，2002年）。
表2. 測量浮游生物環(huán)境中氧濃度的不同方法
使用氧氣微探針測量細菌呼吸可以解決離散測量中遇到的主要問(wèn)題之一：在黑暗培養期間監測氧氣減少。在這項研究中進(jìn)行的27項測量中，只有9項顯示出氧濃度的線(xiàn)性下降，其他的顯示出某種程度上與水的營(yíng)養狀態(tài)相關(guān)的趨勢。這種監控有兩個(gè)主要優(yōu)點(diǎn)。首先，通過(guò)跟蹤氧濃度與時(shí)間的關(guān)系，可以檢測到顯著(zhù)耗氧量的開(kāi)始。由于采用了保護陰極（Revsbech 1989），氧氣微探針不會(huì )消耗氧氣，并且顯示出約0.1μM O2的高精度，該值與在高精度Winkler測量中觀(guān)察到的值相似（見(jiàn)表2）。然而，這種高靈敏度被背景噪聲抵消，背景噪聲通常發(fā)生在用微探針測量氧氣的過(guò)程中。因此，在浮游水域進(jìn)行氧氣測量時(shí)，0.1μM的理論精度實(shí)際上降低到0.5μM O2。
第二個(gè)優(yōu)點(diǎn)是，一旦發(fā)現顯著(zhù)的氧氣減少，就可以大大縮短培養時(shí)間，從而在記錄足夠的數據點(diǎn)時(shí)停止培養。因此，通過(guò)最小化瓶子效應和伴隨的群落變化，在盡可能接近初始原位條件的條件下進(jìn)行測量。
然而，氧微探針的精度不足以測量培養時(shí)間短的貧營(yíng)養水體中的細菌呼吸。對貧營(yíng)養水體中氧濃度的監測表明，只有在培養過(guò)程中細菌活性和生物量增加后，氧微探針才能測量到氧濃度的降低（圖4B）。這清楚地表明，這些水域的呼吸測量仍然存在問(wèn)題，因為目前還沒(méi)有靈敏度足以檢測這些非常低的原位呼吸率的技術(shù)。Gattuso等人（2002年）提出了替代技術(shù)的應用，這將提供更高的氧敏感性，因此可能大大縮短培養時(shí)間，例如使用膜入口離子阱質(zhì)譜法（Cowie和Lloyd，1999年）來(lái)估計呼吸速率。
評論和建議
BGE的測定需要估計細菌產(chǎn)量。這通常是通過(guò)使用放射性標記的亮氨酸或胸腺嘧啶核苷測量蛋白質(zhì)或DNA合成速率來(lái)完成的，盡管也可以使用細菌豐度和大小的變化。通過(guò)加入放射性示蹤劑來(lái)估計細菌產(chǎn)量可以在很短的培養時(shí)間內完成，并且被認為是原位率的一個(gè)很好的代表。然而，BGE是根據比用于測定細菌產(chǎn)量的時(shí)間更長(cháng)的培養時(shí)間內估計的細菌呼吸來(lái)計算的。因此，BGE是根據在兩種不同培養條件下估計的兩種代謝過(guò)程的速率來(lái)計算的，這可能會(huì )使其產(chǎn)生偏差（即，在短時(shí)間間隔內測量的生產(chǎn)速率可能與更長(cháng)時(shí)間范圍內的呼吸速率不一致）。根據培養期間細菌豐度的變化估算細菌凈產(chǎn)量，以進(jìn)行呼吸測量，這是一種替代解決方案。通過(guò)使用非破壞性方法測量氧氣變化，可以在培養結束時(shí)獲得子樣本，以確定細菌的凈生物量。這樣，兩個(gè)過(guò)程將以相同的時(shí)間尺度和相同的孵化條件進(jìn)行估計。
通過(guò)連續監測細菌呼吸測量期間的氧氣變化來(lái)縮短培養時(shí)間的可能性需要以足夠的精度確定細菌凈生物量的產(chǎn)生。為了達到所需的靈敏度，使用表觀(guān)熒光顯微鏡測定細菌數量需要對大量細菌進(jìn)行計數，并使用多個(gè)復制品，特別是在貧營(yíng)養水域。這將大大增加與測量相關(guān)的工作量。流式細胞術(shù)可能是測定呼吸培養期間細菌凈生物量的一種替代技術(shù)。與表面熒光顯微鏡相比，該技術(shù)提供了一種更高靈敏度的細菌數量測量方法（Troussellier等人，1999年；Lemarchand等人，2001年）。此外，流式細胞術(shù)可用于在培養開(kāi)始和結束時(shí)估計細胞的生物體積，甚至蛋白質(zhì)含量（Zubkov等人，1999年），從而更好地計算細菌凈產(chǎn)量，因為在BGE測定的培養過(guò)程中，經(jīng)常報告細菌細胞生物體積的變化（Gattuso等人，2002年）。
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使用氧微電極來(lái)研究細菌的呼吸作用以確定浮游細菌的生長(cháng)速率——摘要
使用氧微電極來(lái)研究細菌的呼吸作用以確定浮游細菌的生長(cháng)速率——材料和程序
